Remove .listener member of controlistener struct

In the new netmgr code, the .listener member was mostly functionally
only duplicating the .exiting member and was unneeded.  This also
resolves following ThreadSanitizer (harmless) warning:

    WARNING: ThreadSanitizer: data race
      Write of size 1 at 0x000000000001 by thread T1:
	#0 control_senddone bin/named/controlconf.c:257:22
	#1 tcp_send_cb lib/isc/netmgr/tcp.c:1027:2
	#2 uv__write_callbacks /home/ondrej/Projects/tsan/libuv/src/unix/stream.c:953:7
	#3 uv__stream_io /home/ondrej/Projects/tsan/libuv/src/unix/stream.c:1330:5
	#4 uv__run_pending /home/ondrej/Projects/tsan/libuv/src/unix/core.c:812:5
	#5 uv_run /home/ondrej/Projects/tsan/libuv/src/unix/core.c:377:19
	#6 nm_thread lib/isc/netmgr/netmgr.c:500:11

      Previous write of size 1 at 0x000000000001 by thread T2:
	#0 control_senddone bin/named/controlconf.c:257:22
	#1 tcp_send_cb lib/isc/netmgr/tcp.c:1027:2
	#2 uv__write_callbacks /home/ondrej/Projects/tsan/libuv/src/unix/stream.c:953:7
	#3 uv__stream_io /home/ondrej/Projects/tsan/libuv/src/unix/stream.c:1330:5
	#4 uv__run_pending /home/ondrej/Projects/tsan/libuv/src/unix/core.c:812:5
	#5 uv_run /home/ondrej/Projects/tsan/libuv/src/unix/core.c:377:19
	#6 nm_thread lib/isc/netmgr/netmgr.c:500:11

      Location is heap block of size 265 at 0x000000000009 allocated by thread T3:
	#0 malloc <null>
	#1 default_memalloc lib/isc/mem.c:713:8
	#2 mem_get lib/isc/mem.c:622:8
	#3 isc___mem_get lib/isc/mem.c:1044:9
	#4 isc__mem_get lib/isc/mem.c:2432:10
	#5 add_listener bin/named/controlconf.c:1133:13
	#6 named_controls_configure bin/named/controlconf.c:1331:6
	#7 load_configuration bin/named/server.c:9133:2
	#8 run_server bin/named/server.c:9771:2
	#9 dispatch lib/isc/task.c:1152:7
	#10 run lib/isc/task.c:1344:2

      Thread T2 (running) created by main thread at:
	#0 pthread_create <null>
	#1 isc_thread_create lib/isc/pthreads/thread.c:73:8
	#2 isc_nm_start lib/isc/netmgr/netmgr.c:223:3
	#3 create_managers bin/named/main.c:909:15
	#4 setup bin/named/main.c:1223:11
	#5 main bin/named/main.c:1523:2

      Thread T2 (running) created by main thread at:
	#0 pthread_create <null>
	#1 isc_thread_create lib/isc/pthreads/thread.c:73:8
	#2 isc_nm_start lib/isc/netmgr/netmgr.c:223:3
	#3 create_managers bin/named/main.c:909:15
	#4 setup bin/named/main.c:1223:11
	#5 main bin/named/main.c:1523:2

      Thread T3 (running) created by main thread at:
	#0 pthread_create <null>
	#1 isc_thread_create lib/isc/pthreads/thread.c:73:8
	#2 isc_taskmgr_create lib/isc/task.c:1434:3
	#3 create_managers bin/named/main.c:915:11
	#4 setup bin/named/main.c:1223:11
	#5 main bin/named/main.c:1523:2

    SUMMARY: ThreadSanitizer: data race bin/named/controlconf.c:257:22 in control_senddone
75 jobs for !4147 with 2164-threadsanitizer-data-race-bin-named-controlconf-c-257-22-in-control_senddone in 17 minutes and 32 seconds (queued for 12 seconds)
latest detached
Status Job ID Name Coverage
  Autoconf
passed #1169133
amd64 linux
autoreconf

00:00:16

 
  Precheck
passed #1169135
amd64 linux
clang-format

00:00:16

passed #1169136
amd64 linux
coccinelle

00:03:10

passed #1169207
linux amd64
danger

00:00:13

passed #1169134
amd64 linux
misc

00:00:15

passed #1169138
amd64 linux
tarball-create

00:01:19

passed #1169137
amd64 linux
danger

00:00:14

 
  Build
passed #1169151
amd64 linux
clang:asan

00:02:03

passed #1169155
amd64 linux
clang:buster:amd64

00:01:03

passed #1169158
amd64 libvirt
clang:freebsd11:amd64

00:01:06

passed #1169159
amd64 libvirt
clang:freebsd12:amd64

00:01:14

passed #1169160
amd64 libvirt
clang:openbsd:amd64

00:02:17

passed #1169153
amd64 linux
clang:tsan

00:01:18

passed #1169139
amd64 linux
gcc:alpine3.12:amd64

00:00:57

passed #1169150
amd64 linux
gcc:asan

00:01:44

passed #1169143
amd64 linux
gcc:buster:amd64

00:00:56

passed #1169140
amd64 linux
gcc:centos7:amd64

00:00:45

passed #1169141
amd64 linux
gcc:centos8:amd64

00:00:56

passed #1169149
amd64 linux
gcc:focal:amd64

00:00:59

passed #1169154
amd64 linux
gcc:mutexatomics

00:01:03

passed #1169145
amd64 linux
gcc:out-of-tree

00:00:55

passed #1169144
amd64 linux
gcc:sid:amd64

00:01:11

passed #1169146
i386 linux
gcc:sid:i386

00:01:01

passed #1169156
amd64 linux
gcc:softhsm2.4

00:00:59

passed #1169157
amd64 linux
gcc:softhsm2.6

00:00:50

passed #1169142
amd64 linux
gcc:stretch:amd64

00:01:03

passed #1169152
amd64 linux
gcc:tsan

00:01:06

passed #1169147
amd64 linux
gcc:tumbleweed:amd64

00:00:51

passed #1169148
amd64 linux
gcc:xenial:amd64

00:00:50

passed #1169161
amd64 windows
msvc:windows:amd64

00:00:45

 
  Unit
passed #1169173
amd64 linux
unit:clang:asan

00:01:15

passed #1169177
amd64 linux
unit:clang:buster:amd64

00:01:04

passed #1169180
amd64 libvirt
unit:clang:freebsd11:amd64

00:01:29

passed #1169181
amd64 libvirt
unit:clang:freebsd12:amd64

00:01:16

passed #1169175
amd64 linux
unit:clang:tsan

00:02:52

passed #1169162
amd64 linux
unit:gcc:alpine3.12:amd64

00:01:01

passed #1169172
amd64 linux
unit:gcc:asan

00:01:16

passed #1169166
amd64 linux
unit:gcc:buster:amd64

00:00:57

passed #1169163
amd64 linux
unit:gcc:centos7:amd64

00:00:55

passed #1169164
amd64 linux
unit:gcc:centos8:amd64

00:00:56

passed #1169171
amd64 linux
unit:gcc:focal:amd64

00:00:54

passed #1169176
amd64 linux
unit:gcc:mutexatomics

00:00:55

passed #1169167
amd64 linux
unit:gcc:sid:amd64

00:01:02

passed #1169168
i386 linux
unit:gcc:sid:i386

00:01:03

passed #1169178
amd64 linux
unit:gcc:softhsm2.4

00:01:03

passed #1169179
amd64 linux
unit:gcc:softhsm2.6

00:00:59

passed #1169165
amd64 linux
unit:gcc:stretch:amd64

00:00:57

passed #1169174
amd64 linux
unit:gcc:tsan

00:03:44

passed #1169169
amd64 linux
unit:gcc:tumbleweed:amd64

00:00:57

passed #1169170
amd64 linux
unit:gcc:xenial:amd64

00:00:57

 
  System
passed #1169193
amd64 linux
system:clang:asan

00:12:07

passed #1169197
amd64 linux
system:clang:buster:amd64

00:11:34

passed #1169200
amd64 libvirt
system:clang:freebsd11:amd64

00:10:09

passed #1169201
amd64 libvirt
system:clang:freebsd12:amd64

00:10:01

failed #1169195
amd64 linux allowed to fail
system:clang:tsan

00:13:37

passed #1169182
amd64 linux
system:gcc:alpine3.12:amd64

00:11:56

passed #1169192
amd64 linux
system:gcc:asan

00:12:37

passed #1169186
amd64 linux
system:gcc:buster:amd64

00:11:04

passed #1169183
amd64 linux
system:gcc:centos7:amd64

00:11:21

passed #1169184
amd64 linux
system:gcc:centos8:amd64

00:11:53

passed #1169191
amd64 linux
system:gcc:focal:amd64

00:11:22

passed #1169196
amd64 linux
system:gcc:mutexatomics

00:11:02

passed #1169187
amd64 linux
system:gcc:sid:amd64

00:10:25

passed #1169188
i386 linux
system:gcc:sid:i386

00:11:26

passed #1169198
amd64 linux
system:gcc:softhsm2.4

00:10:43

passed #1169199
amd64 linux
system:gcc:softhsm2.6

00:11:14

passed #1169185
amd64 linux
system:gcc:stretch:amd64

00:09:45

failed #1169194
amd64 linux allowed to fail
system:gcc:tsan

00:14:23

passed #1169189
amd64 linux
system:gcc:tumbleweed:amd64

00:10:55

passed #1169190
amd64 linux
system:gcc:xenial:amd64

00:10:41

 
  Docs
passed #1169202
amd64 linux
docs

00:00:38

 
  Postcheck
passed #1169206
amd64 linux
cppcheck

00:00:50

passed #1169203
amd64 linux
flake8

00:00:26

passed #1169204
amd64 linux
pylint

00:00:22

passed #1169205
amd64 linux
scan-build

00:04:31

 
Name Stage Failure
failed
system:gcc:tsan System
E:chain:2020-09-21T08:39:46+0000
FAIL chain (exit status: 1)

$ find bin -name 'tsan.*' -exec python3 util/parse_tsan.py {} \;
Uploading artifacts for failed job
Uploading artifacts...
untracked: found 9745 files

Uploading artifacts as "archive" to coordinator... ok
id=1169194 responseStatus=201 Created token=Cxaa8qZZ
ERROR: Job failed: exit code 1
failed
system:clang:tsan System
E:shutdown:2020-09-21T08:39:36+0000
FAIL shutdown (exit status: 1)

$ find bin -name 'tsan.*' -exec python3 util/parse_tsan.py {} \;
Uploading artifacts for failed job
Uploading artifacts...
untracked: found 11224 files

Uploading artifacts as "archive" to coordinator... ok
id=1169195 responseStatus=201 Created token=UcPgW2Bt
ERROR: Job failed: exit code 1