Ignore TSAN errors accessing init_count and header->count

Ignore TSAN errors accessing init_count and header->count

    WARNING: ThreadSanitizer: data race
    Write of size 4 at 0x000000000001 by thread T1 (mutexes: write M1):
    #0 subtractrdataset lib/dns/rbtdb.c:7065:21
    #1 dns_db_subtractrdataset lib/dns/db.c:807:10
    #2 diff_apply lib/dns/diff.c:377:14
    #3 dns_diff_apply lib/dns/diff.c:458:10
    #4 do_one_tuple lib/dns/zone.c:4103:11
    #5 update_one_rr lib/dns/zone.c:4132:10
    #6 keyfetch_done lib/dns/zone.c:9835:4
    #7 dispatch lib/isc/task.c:1157:7
    #8 run lib/isc/task.c:1331:2

    Previous write of size 4 at 0x000000000001 by thread T2 (mutexes: write M2):
    #0 addrdataset lib/dns/rbtdb.c:6869:21
    #1 dns_db_addrdataset lib/dns/db.c:783:10
    #2 addoptout lib/dns/ncache.c:264:10
    #3 dns_ncache_add lib/dns/ncache.c:101:10
    #4 ncache_adderesult lib/dns/resolver.c:5989:12
    #5 ncache_message lib/dns/resolver.c:6165:11
    #6 resquery_response lib/dns/resolver.c:8691:12
    #7 dispatch lib/isc/task.c:1157:7
    #8 run lib/isc/task.c:1331:2