TSAN error to be investigated v9_11

Job #1286053 failed for 5ce19734:

WARNING: ThreadSanitizer: data race 
  Write of size 4 at 0x000000000001 by thread T1 (mutexes: write M1, write M2):
    #0 dns_zone_refresh lib/dns/zone.c:10484
    #1 dns_zone_notifyreceive2 lib/dns/zone.c:14035
    #2 dns_zone_notifyreceive2 lib/dns/zone.c:13886
    #3 ns_notify_start bin/named/notify.c:150
    #4 client_request bin/named/client.c:3125
    #5 dispatch lib/isc/task.c:1157
    #6 run lib/isc/task.c:1331
    #7 <null> <null>

  Previous read of size 4 at 0x000000000001 by thread T2:
    #0 dns_zone_refresh lib/dns/zone.c:10465
    #1 zone_maintenance lib/dns/zone.c:10254
    #2 zone_timer lib/dns/zone.c:13525
    #3 dispatch lib/isc/task.c:1157
    #4 run lib/isc/task.c:1331
    #5 <null> <null>

  Location is heap block of size 2841 at 0x000000000011 allocated by thread T3:
    #0 malloc <null>
    #1 internal_memalloc lib/isc/mem.c:887
    #2 mem_get lib/isc/mem.c:792
    #3 mem_allocateunlocked lib/isc/mem.c:1545
    #4 isc___mem_allocate lib/isc/mem.c:1566
    #5 isc__mem_allocate lib/isc/mem.c:3048
    #6 isc___mem_get lib/isc/mem.c:1304
    #7 isc__mem_get lib/isc/mem.c:3012
    #8 dns_zone_create lib/dns/zone.c:930
    #9 configure_zone server.c:5697
    #10 do_addzone server.c:12471
    #11 ns_server_changezone server.c:12832
    #12 ns_control_docommand bin/named/control.c:205
    #13 control_recvmessage bin/named/controlconf.c:469
    #14 dispatch lib/isc/task.c:1157
    #15 run lib/isc/task.c:1331
    #16 <null> <null>