Address race between zone_settimer and set_key_expiry_warning by

adding missing lock.

    WARNING: ThreadSanitizer: data race
    Read of size 4 at 0x000000000001 by thread T1 (mutexes: read M1, write M2):
    #0 isc_time_isepoch lib/isc/unix/time.c:110
    #1 zone_settimer lib/dns/zone.c:14649
    #2 dns_zone_maintenance lib/dns/zone.c:6281
    #3 dns_zonemgr_forcemaint lib/dns/zone.c:18190
    #4 view_loaded server.c:9654
    #5 call_loaddone lib/dns/zt.c:301
    #6 doneloading lib/dns/zt.c:575
    #7 zone_asyncload lib/dns/zone.c:2259
    #8 task_run lib/isc/task.c:845
    #9 isc_task_run lib/isc/task.c:938
    #10 isc__nm_async_task lib/isc/netmgr/netmgr.c:855
    #11 process_netievent lib/isc/netmgr/netmgr.c:934
    #12 process_queue lib/isc/netmgr/netmgr.c:1003
    #13 process_all_queues lib/isc/netmgr/netmgr.c:775
    #14 async_cb lib/isc/netmgr/netmgr.c:804
    #15 <null> <null>
    #16 isc__trampoline_run lib/isc/trampoline.c:191
    #17 <null> <null>

    Previous write of size 4 at 0x000000000001 by thread T2:
    #0 isc_time_set lib/isc/unix/time.c:93
    #1 set_key_expiry_warning lib/dns/zone.c:6430
    #2 del_sigs lib/dns/zone.c:6711
    #3 zone_resigninc lib/dns/zone.c:7113
    #4 zone_maintenance lib/dns/zone.c:11111
    #5 zone_timer lib/dns/zone.c:14588
    #6 task_run lib/isc/task.c:845
    #7 isc_task_run lib/isc/task.c:938
    #8 isc__nm_async_task lib/isc/netmgr/netmgr.c:855
    #9 process_netievent lib/isc/netmgr/netmgr.c:934
    #10 process_queue lib/isc/netmgr/netmgr.c:1003
    #11 process_all_queues lib/isc/netmgr/netmgr.c:775
    #12 async_cb lib/isc/netmgr/netmgr.c:804
    #13 <null> <null>
    #14 isc__trampoline_run lib/isc/trampoline.c:191
    #15 <null> <null>

    SUMMARY: ThreadSanitizer: data race lib/isc/unix/time.c:110 in isc_time_isepoch

(cherry picked from commit 3d66e97a)
79 jobs for !5157 with 2720-threadsanitizer-data-race-lib-isc-unix-time-c-110-in-isc_time_isepoch-v9_16 in 24 minutes and 28 seconds (queued for 29 seconds)
latest detached
Status Job ID Name Coverage
  Precheck
passed #1783383
amd64 linux
autoreconf

00:00:15

passed #1783385
amd64 linux
clang-format

00:00:19

passed #1783386
amd64 linux
coccinelle

00:03:09

passed #1783387
amd64 linux
danger

00:00:14

passed #1783384
amd64 linux
misc

00:00:14

passed #1783388
amd64 linux
tarball-create

00:00:18

 
  Build
passed #1783402
amd64 linux
clang:asan

00:03:57

passed #1783406
amd64 linux
clang:buster:amd64

00:01:49

passed #1783409
amd64 libvirt
clang:freebsd12:amd64

00:01:37

passed #1783410
amd64 libvirt
clang:freebsd13:amd64

00:03:32

passed #1783411
amd64 libvirt
clang:openbsd:amd64

00:03:27

passed #1783404
amd64 linux
clang:tsan

00:02:19

passed #1783389
amd64 linux
gcc:alpine3.13:amd64

00:01:37

passed #1783401
amd64 linux
gcc:asan

00:03:09

passed #1783399
amd64 linux
gcc:bionic:amd64

00:01:44

passed #1783393
amd64 linux
gcc:buster:amd64

00:01:25

passed #1783390
amd64 linux
gcc:centos7:amd64

00:01:15

passed #1783391
amd64 linux
gcc:centos8:amd64

00:01:29

passed #1783400
amd64 linux
gcc:focal:amd64

00:01:23

passed #1783405
amd64 linux
gcc:mutexatomics

00:01:25

passed #1783395
amd64 linux
gcc:out-of-tree

00:01:17

passed #1783394
amd64 linux
gcc:sid:amd64

00:01:56

passed #1783397
i386 linux
gcc:sid:i386

00:01:28

passed #1783407
amd64 linux
gcc:softhsm2.4

00:01:33

passed #1783408
amd64 linux
gcc:softhsm2.6

00:01:43

passed #1783392
amd64 linux
gcc:stretch:amd64

00:01:50

passed #1783396
amd64 linux
gcc:tarball

00:01:45

passed #1783403
amd64 linux
gcc:tsan

00:01:53

passed #1783398
amd64 linux
gcc:tumbleweed:amd64

00:01:31

passed #1783413
amd64 windows
msvc:windows:amd64

00:01:08

passed #1783412
amd64 linux
nolibtool:sid:amd64

00:01:59

 
  Unit
passed #1783425
amd64 linux
unit:clang:asan

00:01:11

passed #1783429
amd64 linux
unit:clang:buster:amd64

00:00:39

passed #1783432
amd64 libvirt
unit:clang:freebsd12:amd64

00:01:03

passed #1783433
amd64 libvirt
unit:clang:freebsd13:amd64

00:03:01

passed #1783427
amd64 linux
unit:clang:tsan

00:01:47

passed #1783414
amd64 linux
unit:gcc:alpine3.13:amd64

00:00:55

passed #1783424
amd64 linux
unit:gcc:asan

00:01:15

passed #1783422
amd64 linux
unit:gcc:bionic:amd64

00:00:36

passed #1783418
amd64 linux
unit:gcc:buster:amd64

00:00:55

passed #1783415
amd64 linux
unit:gcc:centos7:amd64

00:00:38

passed #1783416
amd64 linux
unit:gcc:centos8:amd64

00:00:37

passed #1783423
amd64 linux
unit:gcc:focal:amd64

00:00:36

passed #1783428
amd64 linux
unit:gcc:mutexatomics

00:00:33

passed #1783419
amd64 linux
unit:gcc:sid:amd64

00:00:35

passed #1783420
i386 linux
unit:gcc:sid:i386

00:00:47

passed #1783430
amd64 linux
unit:gcc:softhsm2.4

00:00:35

passed #1783431
amd64 linux
unit:gcc:softhsm2.6

00:00:41

passed #1783417
amd64 linux
unit:gcc:stretch:amd64

00:00:34

passed #1783426
amd64 linux
unit:gcc:tsan

00:01:36

passed #1783421
amd64 linux
unit:gcc:tumbleweed:amd64

00:00:36

passed #1783434
amd64 linux
unit:nolibtool:sid:amd64

00:00:49

 
  System
passed #1783446
amd64 linux
system:clang:asan

00:13:27

passed #1783450
amd64 linux
system:clang:buster:amd64

00:11:37

failed #1783453
amd64 libvirt
system:clang:freebsd12:amd64

00:12:03

passed #1783454
amd64 libvirt
system:clang:freebsd13:amd64

00:12:44

passed #1783448
amd64 linux
system:clang:tsan

00:15:02

passed #1783435
amd64 linux
system:gcc:alpine3.13:amd64

00:11:51

passed #1783445
amd64 linux
system:gcc:asan

00:13:57

passed #1783443
amd64 linux
system:gcc:bionic:amd64

00:10:42

passed #1783439
amd64 linux
system:gcc:buster:amd64

00:13:13

passed #1783436
amd64 linux
system:gcc:centos7:amd64

00:12:08

passed #1783437
amd64 linux
system:gcc:centos8:amd64

00:11:49

passed #1783444
amd64 linux
system:gcc:focal:amd64

00:11:09

passed #1783449
amd64 linux
system:gcc:mutexatomics

00:11:23

passed #1783440
amd64 linux
system:gcc:sid:amd64

00:10:35

passed #1783441
i386 linux
system:gcc:sid:i386

00:09:34

passed #1783451
amd64 linux
system:gcc:softhsm2.4

00:11:37

passed #1783452
amd64 linux
system:gcc:softhsm2.6

00:11:56

passed #1783438
amd64 linux
system:gcc:stretch:amd64

00:11:40

passed #1783447
amd64 linux
system:gcc:tsan

00:15:29

passed #1783442
amd64 linux
system:gcc:tumbleweed:amd64

00:11:47

passed #1783455
amd64 linux
system:nolibtool:sid:amd64

00:11:39

 
  Docs
passed #1783456
amd64 linux
docs

00:02:11

 
  Postcheck
passed #1783460
amd64 linux
cppcheck

00:00:21

passed #1783457
amd64 linux
flake8

00:00:19

passed #1783461
amd64 linux
gcov

00:00:33

76.0%
passed #1783458
amd64 linux
pylint

00:00:23

passed #1783459
amd64 linux
scan-build

00:08:53

 
Name Stage Failure
failed
system:clang:freebsd12:amd64 System
No job log