Lock access to listener->connections

as it is accessed from multiple threads with libuv.

    WARNING: ThreadSanitizer: data race
    Write of size 8 at 0x000000000001 by thread T1:
    #0 conn_reset bin/named/controlconf.c:574
    #1 isc_nmhandle_detach netmgr/netmgr.c:1257
    #2 isc__nm_uvreq_put netmgr/netmgr.c:1389
    #3 tcp_send_cb netmgr/tcp.c:1030
    #4 <null> <null>
    #5 <null> <null>

    Previous read of size 8 at 0x000000000001 by thread T2:
    #0 conn_reset bin/named/controlconf.c:574
    #1 isc_nmhandle_detach netmgr/netmgr.c:1257
    #2 control_recvmessage bin/named/controlconf.c:556
    #3 recv_data lib/isccc/ccmsg.c:110
    #4 isc__nm_tcp_shutdown netmgr/tcp.c:1161
    #5 shutdown_walk_cb netmgr/netmgr.c:1511
    #6 uv_walk <null>
    #7 process_queue netmgr/netmgr.c:656
    #8 process_normal_queue netmgr/netmgr.c:582
    #9 process_queues netmgr/netmgr.c:590
    #10 async_cb netmgr/netmgr.c:548
    #11 <null> <null>
    #12 <null> <null>

    Location is heap block of size 265 at 0x000000000017 allocated by thread T3:
    #0 malloc <null>
    #1 default_memalloc lib/isc/mem.c:713
    #2 mem_get lib/isc/mem.c:622
    #3 isc___mem_get lib/isc/mem.c:1044
    #4 isc__mem_get lib/isc/mem.c:2432
    #5 add_listener bin/named/controlconf.c:1127
    #6 named_controls_configure bin/named/controlconf.c:1324
    #7 load_configuration bin/named/server.c:9181
    #8 run_server bin/named/server.c:9819
    #9 dispatch lib/isc/task.c:1152
    #10 run lib/isc/task.c:1344
    #11 <null> <null>

    Thread T1 (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create pthreads/thread.c:73
    #2 isc_nm_start netmgr/netmgr.c:232
    #3 create_managers bin/named/main.c:909
    #4 setup bin/named/main.c:1223
    #5 main bin/named/main.c:1523

    Thread T2 (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create pthreads/thread.c:73
    #2 isc_nm_start netmgr/netmgr.c:232
    #3 create_managers bin/named/main.c:909
    #4 setup bin/named/main.c:1223
    #5 main bin/named/main.c:1523

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

    SUMMARY: ThreadSanitizer: data race bin/named/controlconf.c:574 in conn_reset
75 jobs for !4206 with 2192-tsan-error-accessing-listener-connections in 16 minutes and 25 seconds (queued for 8 seconds)
detached
Status Job ID Name Coverage
  Autoconf
passed #1191910
amd64 linux
autoreconf

00:00:17

 
  Precheck
passed #1191912
amd64 linux
clang-format

00:00:16

passed #1191913
amd64 linux
coccinelle

00:03:34

passed #1191986
linux amd64
danger

00:00:13

passed #1191911
amd64 linux
misc

00:00:14

passed #1191915
amd64 linux
tarball-create

00:01:43

failed #1191914
amd64 linux
danger

00:00:14

 
  Build
passed #1191928
amd64 linux
clang:asan

00:02:07

passed #1191932
amd64 linux
clang:buster:amd64

00:01:03

passed #1191935
amd64 libvirt
clang:freebsd11:amd64

00:01:54

passed #1191936
amd64 libvirt
clang:freebsd12:amd64

00:01:30

passed #1191937
amd64 libvirt
clang:openbsd:amd64

00:02:30

passed #1191930
amd64 linux
clang:tsan

00:01:23

passed #1191916
amd64 linux
gcc:alpine3.12:amd64

00:01:01

passed #1191927
amd64 linux
gcc:asan

00:01:43

passed #1191920
amd64 linux
gcc:buster:amd64

00:00:50

passed #1191917
amd64 linux
gcc:centos7:amd64

00:00:46

passed #1191918
amd64 linux
gcc:centos8:amd64

00:01:00

passed #1191926
amd64 linux
gcc:focal:amd64

00:00:59

passed #1191931
amd64 linux
gcc:mutexatomics

00:00:53

passed #1191922
amd64 linux
gcc:out-of-tree

00:01:04

passed #1191921
amd64 linux
gcc:sid:amd64

00:01:10

passed #1191923
i386 linux
gcc:sid:i386

00:01:01

passed #1191933
amd64 linux
gcc:softhsm2.4

00:01:01

passed #1191934
amd64 linux
gcc:softhsm2.6

00:00:50

passed #1191919
amd64 linux
gcc:stretch:amd64

00:01:00

passed #1191929
amd64 linux
gcc:tsan

00:01:17

passed #1191924
amd64 linux
gcc:tumbleweed:amd64

00:00:56

passed #1191925
amd64 linux
gcc:xenial:amd64

00:01:02

passed #1191938
amd64 windows
msvc:windows:amd64

00:01:04

 
  Unit
passed #1191950
amd64 linux
unit:clang:asan

00:01:21

passed #1191954
amd64 linux
unit:clang:buster:amd64

00:00:57

passed #1191957
amd64 libvirt
unit:clang:freebsd11:amd64

00:01:27

passed #1191958
amd64 libvirt
unit:clang:freebsd12:amd64

00:01:20

passed #1191952
amd64 linux
unit:clang:tsan

00:02:54

passed #1191939
amd64 linux
unit:gcc:alpine3.12:amd64

00:01:02

passed #1191949
amd64 linux
unit:gcc:asan

00:01:24

passed #1191943
amd64 linux
unit:gcc:buster:amd64

00:01:02

passed #1191940
amd64 linux
unit:gcc:centos7:amd64

00:00:57

passed #1191941
amd64 linux
unit:gcc:centos8:amd64

00:01:02

passed #1191948
amd64 linux
unit:gcc:focal:amd64

00:00:59

passed #1191953
amd64 linux
unit:gcc:mutexatomics

00:01:00

passed #1191944
amd64 linux
unit:gcc:sid:amd64

00:00:59

passed #1191945
i386 linux
unit:gcc:sid:i386

00:01:06

passed #1191955
amd64 linux
unit:gcc:softhsm2.4

00:00:59

passed #1191956
amd64 linux
unit:gcc:softhsm2.6

00:01:03

passed #1191942
amd64 linux
unit:gcc:stretch:amd64

00:01:01

passed #1191951
amd64 linux
unit:gcc:tsan

00:03:43

passed #1191946
amd64 linux
unit:gcc:tumbleweed:amd64

00:00:56

passed #1191947
amd64 linux
unit:gcc:xenial:amd64

00:00:57

 
  System
passed #1191970
amd64 linux
system:clang:asan

00:12:10

passed #1191974
amd64 linux
system:clang:buster:amd64

00:10:27

passed #1191977
amd64 libvirt
system:clang:freebsd11:amd64

00:09:59

failed #1191978
amd64 libvirt
system:clang:freebsd12:amd64

00:10:29

passed #1191972
amd64 linux
system:clang:tsan

00:13:33

passed #1191959
amd64 linux
system:gcc:alpine3.12:amd64

00:12:10

passed #1191969
amd64 linux
system:gcc:asan

00:11:57

passed #1191963
amd64 linux
system:gcc:buster:amd64

00:11:16

passed #1191960
amd64 linux
system:gcc:centos7:amd64

00:11:16

passed #1191961
amd64 linux
system:gcc:centos8:amd64

00:11:37

passed #1191968
amd64 linux
system:gcc:focal:amd64

00:11:12

passed #1191973
amd64 linux
system:gcc:mutexatomics

00:10:01

passed #1191964
amd64 linux
system:gcc:sid:amd64

00:10:39

passed #1191965
i386 linux
system:gcc:sid:i386

00:11:11

passed #1191975
amd64 linux
system:gcc:softhsm2.4

00:10:41

passed #1191976
amd64 linux
system:gcc:softhsm2.6

00:10:39

passed #1191962
amd64 linux
system:gcc:stretch:amd64

00:11:18

passed #1191971
amd64 linux
system:gcc:tsan

00:14:00

passed #1191966
amd64 linux
system:gcc:tumbleweed:amd64

00:10:30

passed #1191967
amd64 linux
system:gcc:xenial:amd64

00:10:41

 
  Docs
passed #1191979
amd64 linux
docs

00:00:41

 
  Postcheck
passed #1191983
amd64 linux
cppcheck

00:00:52

passed #1191980
amd64 linux
flake8

00:00:24

passed #1191981
amd64 linux
pylint

00:00:32

passed #1191982
amd64 linux
scan-build

00:04:14

 
Name Stage Failure
failed
system:clang:freebsd12:amd64 System
$ test -n "${OUT_OF_TREE_WORKSPACE}" && mv "${OUT_OF_TREE_WORKSPACE}" "${CI_PROJECT_DIR}"
Uploading artifacts for failed job
Uploading artifacts...
Runtime platform
arch=amd64 os=freebsd pid=51066 revision=86ad88ea version=13.3.0
untracked: found 1578 files

Uploading artifacts as "archive" to coordinator... ok
id=1191978 responseStatus=201 Created token=C5DhxcnB
Cleaning up file based variables
Unsupported run stage 'cleanup_file_variables'
ERROR: Job failed: exit status 1