9.11 zt_test data race

WARNING: ThreadSanitizer: data race 
  Read of size 1 at 0x000000000001 by main thread:
    #0 asyncload_zone lib/dns/tests/zt_test.c:206
    #1 <null> <null>
    #2 __libc_start_main ../csu/libc-start.c:308

  Previous write of size 1 at 0x000000000001 by thread T1:
    #0 load_done lib/dns/tests/zt_test.c:89
    #1 zone_asyncload lib/dns/zone.c:2243
    #2 dispatch lib/isc/task.c:1157
    #3 run lib/isc/task.c:1331
    #4 <null> <null>

  Location is stack of main thread.

  Location is global '<null>' at 0x000000000000

  Thread T1 (running) created by main thread at:
    #0 pthread_create <null>
    #1 isc_thread_create lib/isc/pthreads/thread.c:60
    #2 isc__taskmgr_create lib/isc/task.c:1468
    #3 isc_taskmgr_create lib/isc/task.c:2109
    #4 create_managers lib/dns/tests/dnstest.c:118
    #5 dns_test_begin lib/dns/tests/dnstest.c:192
    #6 _setup lib/dns/tests/zt_test.c:56
    #7 <null> <null>
    #8 __libc_start_main ../csu/libc-start.c:308

SUMMARY: ThreadSanitizer: data race lib/dns/tests/zt_test.c:206 in asyncload_zone