Lock zone before calling zone_namerd_tostr()

WARNING: ThreadSanitizer: data race
    Read of size 8 at 0x000000000001 by thread T1:
    #0 inline_raw lib/dns/zone.c:1375
    #1 zone_namerd_tostr lib/dns/zone.c:15316
    #2 dns_zone_name lib/dns/zone.c:15391
    #3 xfrin_log lib/dns/xfrin.c:1605
    #4 xfrin_destroy lib/dns/xfrin.c:1477
    #5 dns_xfrin_detach lib/dns/xfrin.c:739
    #6 xfrin_connect_done lib/dns/xfrin.c:970
    #7 tcpdnsconnect_cb netmgr/tcpdns.c:786
    #8 tcp_connect_cb netmgr/tcp.c:292
    #9 <null> <null>
    #10 <null> <null>

    Previous write of size 8 at 0x000000000001 by thread T2 (mutexes: write M1):
    #0 zone_shutdown lib/dns/zone.c:14462
    #1 dispatch lib/isc/task.c:1152
    #2 run lib/isc/task.c:1344
    #3 <null> <null>

    Location is heap block of size 2769 at 0x000000000013 allocated by thread T3:
    #0 malloc <null>
    #1 default_memalloc lib/isc/mem.c:713
    #2 mem_get lib/isc/mem.c:622
    #3 mem_allocateunlocked lib/isc/mem.c:1268
    #4 isc___mem_allocate lib/isc/mem.c:1288
    #5 isc__mem_allocate lib/isc/mem.c:2453
    #6 isc___mem_get lib/isc/mem.c:1037
    #7 isc__mem_get lib/isc/mem.c:2432
    #8 dns_zone_create lib/dns/zone.c:984
    #9 configure_zone bin/named/server.c:6502
    #10 do_addzone bin/named/server.c:13391
    #11 named_server_changezone bin/named/server.c:13788
    #12 named_control_docommand bin/named/control.c:207
    #13 control_command bin/named/controlconf.c:392
    #14 dispatch lib/isc/task.c:1152
    #15 run lib/isc/task.c:1344
    #16 <null> <null>

lib/dns/zone.c

@@ -15388,7 +15388,10 @@ void
 dns_zone_name(dns_zone_t *zone, char *buf, size_t length) {
 	REQUIRE(DNS_ZONE_VALID(zone));
 	REQUIRE(buf != NULL);
+
+	LOCK_ZONE(zone);
 	zone_namerd_tostr(zone, buf, length);
+	UNLOCK_ZONE(zone);
 }
 
 void