Exclude isc_mem_isovermem from ThreadSanitizer

The .is_overmem member of isc_mem_t structure is intentionally accessed
unlocked as 100% accuracy isn't necessary here.

Without the attribute, following TSAN warning would show up:

    WARNING: ThreadSanitizer: data race
      Write of size 1 at 0x000000000001 by thread T1 (mutexes: write M1, write M2):
	#0 isc___mem_put lib/isc/mem.c:1119:19
	#1 isc__mem_put lib/isc/mem.c:2439:2
	#2 dns_rdataslab_fromrdataset lib/dns/rdataslab.c:327:2
	#3 addrdataset lib/dns/rbtdb.c:6761:11
	#4 dns_db_addrdataset lib/dns/db.c:719:10
	#5 cache_name lib/dns/resolver.c:6538:13
	#6 cache_message lib/dns/resolver.c:6628:14
	#7 resquery_response lib/dns/resolver.c:7883:13
	#8 dispatch lib/isc/task.c:1152:7
	#9 run lib/isc/task.c:1344:2

      Previous read of size 1 at 0x000000000001 by thread T2 (mutexes: write M3):
	#0 isc_mem_isovermem lib/isc/mem.c:1553:15
	#1 addrdataset lib/dns/rbtdb.c:6866:25
	#2 dns_db_addrdataset lib/dns/db.c:719:10
	#3 addoptout lib/dns/ncache.c:281:10
	#4 dns_ncache_add lib/dns/ncache.c:101:10
	#5 ncache_adderesult lib/dns/resolver.c:6668:12
	#6 ncache_message lib/dns/resolver.c:6845:11
	#7 rctx_ncache lib/dns/resolver.c:9174:11
	#8 resquery_response lib/dns/resolver.c:7894:2
	#9 dispatch lib/isc/task.c:1152:7
	#10 run lib/isc/task.c:1344:2

      Location is heap block of size 328 at 0x000000000020 allocated by thread T3:
	#0 malloc <null>
	#1 default_memalloc lib/isc/mem.c:713:8
	#2 mem_create lib/isc/mem.c:763:8
	#3 isc_mem_create lib/isc/mem.c:2425:2
	#4 configure_view bin/named/server.c:4494:4
	#5 load_configuration bin/named/server.c:9062:3
	#6 run_server bin/named/server.c:9771:2
	#7 dispatch lib/isc/task.c:1152:7
	#8 run lib/isc/task.c:1344:2

    [...]

    SUMMARY: ThreadSanitizer: data race lib/isc/mem.c:1119:19 in isc___mem_put

(cherry picked from commit 0110d1ab)
85 jobs for !4143 with 2163-threadsanitizer-data-race-lib-isc-mem-c-1119-19-in-isc___mem_put-v9_16 in 32 minutes and 34 seconds (queued for 10 seconds)
latest detached
Status Job ID Name Coverage
  Precheck
passed #1163540
amd64 linux
autoreconf

00:01:12

passed #1163542
amd64 linux
clang-format

00:01:16

passed #1163543
amd64 linux
coccinelle

00:03:09

passed #1163871
amd64 linux
danger

00:00:13

passed #1163541
amd64 linux
misc

00:00:12

failed #1163712
linux amd64
danger

00:00:11

failed #1163544
amd64 linux
danger

00:00:13

 
  Build
passed #1163558
amd64 linux
clang:asan

00:03:47

passed #1163562
amd64 linux
clang:buster:amd64

00:01:48

passed #1163565
amd64 libvirt
clang:freebsd11:amd64

00:01:46

passed #1163566
amd64 libvirt
clang:freebsd12:amd64

00:01:45

passed #1163567
amd64 libvirt
clang:openbsd:amd64

00:04:23

passed #1163560
amd64 linux
clang:tsan

00:02:13

passed #1163545
amd64 linux
gcc:alpine3.12:amd64

00:01:38

passed #1163557
amd64 linux
gcc:asan

00:03:22

passed #1163550
amd64 linux
gcc:buster:amd64

00:01:36

passed #1163546
amd64 linux
gcc:centos6:amd64

00:01:43

passed #1163547
amd64 linux
gcc:centos7:amd64

00:01:30

passed #1163548
amd64 linux
gcc:centos8:amd64

00:01:33

passed #1163556
amd64 linux
gcc:focal:amd64

00:01:35

passed #1163561
amd64 linux
gcc:mutexatomics

00:01:36

passed #1163552
amd64 linux
gcc:out-of-tree

00:01:31

passed #1163551
amd64 linux
gcc:sid:amd64

00:04:56

passed #1163553
i386 linux
gcc:sid:i386

00:04:09

passed #1163563
amd64 linux
gcc:softhsm2.4

00:01:34

passed #1163564
amd64 linux
gcc:softhsm2.6

00:01:45

passed #1163549
amd64 linux
gcc:stretch:amd64

00:01:51

passed #1163559
amd64 linux
gcc:tsan

00:02:04

passed #1163554
amd64 linux
gcc:tumbleweed:amd64

00:01:35

passed #1163555
amd64 linux
gcc:xenial:amd64

00:01:50

passed #1163569
amd64 windows
msvc:windows:amd64

00:00:55

passed #1163568
amd64 linux
nolibtool:sid:amd64

00:02:06

 
  Unit
passed #1163582
amd64 linux
unit:clang:asan

00:00:52

passed #1163586
amd64 linux
unit:clang:buster:amd64

00:00:31

passed #1163589
amd64 libvirt
unit:clang:freebsd11:amd64

00:01:02

passed #1163870
libvirt amd64
unit:clang:freebsd12:amd64

00:01:02

passed #1163584
amd64 linux
unit:clang:tsan

00:01:31

passed #1163570
amd64 linux
unit:gcc:alpine3.12:amd64

00:00:50

passed #1163581
amd64 linux
unit:gcc:asan

00:00:49

passed #1163575
amd64 linux
unit:gcc:buster:amd64

00:00:35

passed #1163571
amd64 linux
unit:gcc:centos6:amd64

00:00:38

passed #1163572
amd64 linux
unit:gcc:centos7:amd64

00:00:38

passed #1163573
amd64 linux
unit:gcc:centos8:amd64

00:00:38

passed #1163580
amd64 linux
unit:gcc:focal:amd64

00:00:38

passed #1163585
amd64 linux
unit:gcc:mutexatomics

00:00:33

passed #1163576
amd64 linux
unit:gcc:sid:amd64

00:00:35

passed #1163577
i386 linux
unit:gcc:sid:i386

00:00:46

passed #1163587
amd64 linux
unit:gcc:softhsm2.4

00:00:34

passed #1163588
amd64 linux
unit:gcc:softhsm2.6

00:00:36

passed #1163574
amd64 linux
unit:gcc:stretch:amd64

00:00:34

passed #1163583
amd64 linux
unit:gcc:tsan

00:01:48

passed #1163578
amd64 linux
unit:gcc:tumbleweed:amd64

00:00:38

passed #1163579
amd64 linux
unit:gcc:xenial:amd64

00:00:36

passed #1163591
amd64 linux
unit:nolibtool:sid:amd64

00:00:48

failed #1163590
amd64 libvirt
unit:clang:freebsd12:amd64

00:05:59

passed #1163869
libvirt amd64
unit:clang:freebsd12:amd64

00:01:03

 
  System
passed #1163604
amd64 linux
system:clang:asan

00:12:24

passed #1163608
amd64 linux
system:clang:buster:amd64

00:11:12

passed #1163611
amd64 libvirt
system:clang:freebsd11:amd64

00:10:29

passed #1163612
amd64 libvirt
system:clang:freebsd12:amd64

00:10:07

failed #1163606
amd64 linux allowed to fail
system:clang:tsan

00:14:45

passed #1163592
amd64 linux
system:gcc:alpine3.12:amd64

00:11:50

passed #1163603
amd64 linux
system:gcc:asan

00:12:42

passed #1163597
amd64 linux
system:gcc:buster:amd64

00:11:52

passed #1163593
amd64 linux
system:gcc:centos6:amd64

00:11:14

passed #1163594
amd64 linux
system:gcc:centos7:amd64

00:11:30

passed #1163872
linux amd64
system:gcc:centos8:amd64

00:11:08

passed #1163602
amd64 linux
system:gcc:focal:amd64

00:11:37

passed #1163607
amd64 linux
system:gcc:mutexatomics

00:10:32

passed #1163598
amd64 linux
system:gcc:sid:amd64

00:10:53

passed #1163873
linux i386
system:gcc:sid:i386

00:10:07

passed #1163609
amd64 linux
system:gcc:softhsm2.4

00:10:44

passed #1163610
amd64 linux
system:gcc:softhsm2.6

00:11:43

passed #1163596
amd64 linux
system:gcc:stretch:amd64

00:10:33

failed #1163605
amd64 linux allowed to fail
system:gcc:tsan

00:14:49

passed #1163600
amd64 linux
system:gcc:tumbleweed:amd64

00:11:28

passed #1163601
amd64 linux
system:gcc:xenial:amd64

00:10:49

passed #1163613
amd64 linux
system:nolibtool:sid:amd64

00:11:26

failed #1163595
amd64 linux
system:gcc:centos8:amd64

00:18:52

failed #1163599
i386 linux
system:gcc:sid:i386

00:16:58

 
  Docs
passed #1163614
amd64 linux
docs

00:02:08

 
  Postcheck
passed #1163618
amd64 linux
cppcheck

00:00:18

passed #1163615
amd64 linux
flake8

00:00:16

passed #1163616
amd64 linux
pylint

00:00:21

passed #1163617
amd64 linux
scan-build

00:09:11

 
Name Stage Failure
failed
system:clang:tsan System
make: *** [Makefile:491: test] Error 1
Running after_script
Running after script...
$ find bin -name 'tsan.*' -exec python3 util/parse_tsan.py {} \;
Uploading artifacts for failed job
Uploading artifacts...
untracked: found 11109 files

Uploading artifacts as "archive" to coordinator... ok
id=1163606 responseStatus=201 Created token=3pMtyx-T
ERROR: Job failed: exit code 1
failed
system:gcc:tsan System
make: *** [Makefile:491: test] Error 1
Running after_script
Running after script...
$ find bin -name 'tsan.*' -exec python3 util/parse_tsan.py {} \;
Uploading artifacts for failed job
Uploading artifacts...
untracked: found 11407 files

Uploading artifacts as "archive" to coordinator... ok
id=1163605 responseStatus=201 Created token=x93ReKue
ERROR: Job failed: exit code 1