illumos gate

It appears the cause of the smbd_dc_monitor thread getting stuck is
contention for the mutex smbrdr_screate_mtx in
usr/src/lib/smbsrv/libsmbrdr/common/smbrdr_session.c
Anything attempting to use this connection will hold that mutex
for the duration of the connection setup attempt, which may take
several minutes before it fails and gives up the mutex.

The things most often blocking progress of smb_ddiscover_main were:
1: libmlsvc: netlogon_logon(), trying to open a pipe to the current DC.
2: smbd: smbd_dc_monitor() / dssetup_check_service() ditto, and
3: occasionally: mlsvc_timecheck(), opening /pipe/srvsvc to the DC.

For now, make all of these "give way" to the dc location thread,
because that will sometimes change who these other threads
will try to communicate with.

http://cr.illumos.org/view/xmjid46h/