Lock on msg == SELECT_POKE_CLOSE as it triggers a tsan error

Lock on msg == SELECT_POKE_CLOSE as it triggers a tsan error

WARNING: ThreadSanitizer: data race (pid=1941)
  Write of size 4 at 0x7ba40000f050 by main thread (mutexes: write M1100, write M75):
    #0 socket_create /builds/isc-projects/bind9/1126G:3009:29 (libisc.so.1105+0x60822)
    #1 isc__socket_create /builds/isc-projects/bind9/lib/isc/unix/socket.c:3043:10 (libisc.so.1105+0x60583)
    #2 isc_socket_create /builds/isc-projects/bind9/lib/isc/unix/./../socket_api.c:105:11 (libisc.so.1105+0x6a4a0)
    #3 open_socket /builds/isc-projects/bind9/lib/dns/dispatch.c:1708:12 (libdns.so.1110+0x7491c)
    #4 get_udpsocket /builds/isc-projects/bind9/lib/dns/dispatch.c:2904:13 (libdns.so.1110+0x745ec)
    #5 dispatch_createudp /builds/isc-projects/bind9/lib/dns/dispatch.c:2994:12 (libdns.so.1110+0x6e159)
    #6 dns_dispatch_getudp_dup /builds/isc-projects/bind9/lib/dns/dispatch.c:2823:11 (libdns.so.1110+0x6d8f2)
    #7 dns_dispatch_getudp /builds/isc-projects/bind9/lib/dns/dispatch.c:2849:10 (libdns.so.1110+0x6e99e)
    #8 make_dispatchset /builds/isc-projects/bind9/lib/dns/tests/dispatch_test.c:81:11 (dispatch_test+0x4ba8fc)
    #9 dispatchset_create /builds/isc-projects/bind9/lib/dns/tests/dispatch_test.c:115:11 (dispatch_test+0x4b9f99)
    #10 <null> <null> (libcmocka.so.0+0x50d8)
    #11 __libc_start_main /build/glibc-vjB4T1/glibc-2.28/csu/../csu/libc-start.c:308:16 (libc.so.6+0x2409a)

  Previous write of size 4 at 0x7ba40000f050 by thread T14:
    #0 wakeup_socket /builds/isc-projects/bind9/lib/isc/unix/socket.c:1126:24 (libisc.so.1105+0x70181)
    #1 process_ctlfd /builds/isc-projects/bind9/lib/isc/unix/socket.c:4252:3 (libisc.so.1105+0x6c048)
    #2 process_fds /builds/isc-projects/bind9/lib/isc/unix/socket.c:4156:10 (libisc.so.1105+0x6bcb4)
    #3 watcher /builds/isc-projects/bind9/lib/isc/unix/socket.c:4395:10 (libisc.so.1105+0x64188)

  Location is heap block of size 16385 at 0x7ba40000f000 allocated by main thread:
    #0 malloc <null> (dispatch_test+0x42b7c4)
    #1 internal_memalloc /builds/isc-projects/bind9/lib/isc/mem.c:887:8 (libisc.so.1105+0x37e38)
    #2 mem_get /builds/isc-projects/bind9/lib/isc/mem.c:792:8 (libisc.so.1105+0x32c2c)
    #3 isc___mem_get /builds/isc-projects/bind9/lib/isc/mem.c:1310:9 (libisc.so.1105+0x325d7)
    #4 isc__mem_get /builds/isc-projects/bind9/lib/isc/mem.c:3012:11 (libisc.so.1105+0x34f80)
    #5 isc__socketmgr_create2 /builds/isc-projects/bind9/lib/isc/unix/socket.c:4697:21 (libisc.so.1105+0x6374f)
    #6 isc__socketmgr_create /builds/isc-projects/bind9/lib/isc/unix/socket.c:4651:10 (libisc.so.1105+0x635f2)
    #7 isc_socketmgr_create /builds/isc-projects/bind9/lib/isc/unix/./../socket_api.c:74:11 (libisc.so.1105+0x6a2c7)
    #8 create_managers /builds/isc-projects/bind9/lib/dns/tests/dnstest.c:120:2 (dispatch_test+0x4bb28a)
    #9 dns_test_begin /builds/isc-projects/bind9/lib/dns/tests/dnstest.c:192:3 (dispatch_test+0x4bb182)
    #10 _setup /builds/isc-projects/bind9/lib/dns/tests/dispatch_test.c:53:11 (dispatch_test+0x4b9ff8)
    #11 <null> <null> (libcmocka.so.0+0x51e2)
    #12 __libc_start_main /build/glibc-vjB4T1/glibc-2.28/csu/../csu/libc-start.c:308:16 (libc.so.6+0x2409a)

  Mutex M1100 (0x7b5000000230) created at:
    #0 pthread_mutex_init <null> (dispatch_test+0x42e60d)
    #1 isc__mutex_init /builds/isc-projects/bind9/lib/isc/pthreads/mutex.c:287:8 (libisc.so.1105+0x72317)
    #2 dns_dispatchmgr_create /builds/isc-projects/bind9/lib/dns/dispatch.c:1778:11 (libdns.so.1110+0x6a055)
    #3 make_dispatchset /builds/isc-projects/bind9/lib/dns/tests/dispatch_test.c:75:11 (dispatch_test+0x4ba883)
    #4 dispatchset_create /builds/isc-projects/bind9/lib/dns/tests/dispatch_test.c:115:11 (dispatch_test+0x4b9f99)
    #5 <null> <null> (libcmocka.so.0+0x50d8)
    #6 __libc_start_main /build/glibc-vjB4T1/glibc-2.28/csu/../csu/libc-start.c:308:16 (libc.so.6+0x2409a)

  Mutex M75 (0x7bb800000320) created at:
    #0 pthread_mutex_init <null> (dispatch_test+0x42e60d)
    #1 isc__mutex_init /builds/isc-projects/bind9/lib/isc/pthreads/mutex.c:287:8 (libisc.so.1105+0x72317)
    #2 isc__socketmgr_create2 /builds/isc-projects/bind9/lib/isc/unix/socket.c:4728:12 (libisc.so.1105+0x63914)
    #3 isc__socketmgr_create /builds/isc-projects/bind9/lib/isc/unix/socket.c:4651:10 (libisc.so.1105+0x635f2)
    #4 isc_socketmgr_create /builds/isc-projects/bind9/lib/isc/unix/./../socket_api.c:74:11 (libisc.so.1105+0x6a2c7)
    #5 create_managers /builds/isc-projects/bind9/lib/dns/tests/dnstest.c:120:2 (dispatch_test+0x4bb28a)
    #6 dns_test_begin /builds/isc-projects/bind9/lib/dns/tests/dnstest.c:192:3 (dispatch_test+0x4bb182)
    #7 _setup /builds/isc-projects/bind9/lib/dns/tests/dispatch_test.c:53:11 (dispatch_test+0x4b9ff8)
    #8 <null> <null> (libcmocka.so.0+0x51e2)
    #9 __libc_start_main /build/glibc-vjB4T1/glibc-2.28/csu/../csu/libc-start.c:308:16 (libc.so.6+0x2409a)

  Thread T14 'isc-socket' (tid=1969, running) created by main thread at:
    #0 pthread_create <null> (dispatch_test+0x42d08b)
    #1 isc_thread_create /builds/isc-projects/bind9/lib/isc/pthreads/thread.c:60:8 (libisc.so.1105+0x72488)
    #2 isc__socketmgr_create2 /builds/isc-projects/bind9/lib/isc/unix/socket.c:4787:6 (libisc.so.1105+0x63cc6)
    #3 isc__socketmgr_create /builds/isc-projects/bind9/lib/isc/unix/socket.c:4651:10 (libisc.so.1105+0x635f2)
    #4 isc_socketmgr_create /builds/isc-projects/bind9/lib/isc/unix/./../socket_api.c:74:11 (libisc.so.1105+0x6a2c7)
    #5 create_managers /builds/isc-projects/bind9/lib/dns/tests/dnstest.c:120:2 (dispatch_test+0x4bb28a)
    #6 dns_test_begin /builds/isc-projects/bind9/lib/dns/tests/dnstest.c:192:3 (dispatch_test+0x4bb182)
    #7 _setup /builds/isc-projects/bind9/lib/dns/tests/dispatch_test.c:53:11 (dispatch_test+0x4b9ff8)
    #8 <null> <null> (libcmocka.so.0+0x51e2)
    #9 __libc_start_main /build/glibc-vjB4T1/glibc-2.28/csu/../csu/libc-start.c:308:16 (libc.so.6+0x2409a)

SUMMARY: ThreadSanitizer: data race /builds/isc-projects/bind9/lib/isc/unix/socket.c:3009:29 in socket_create