Allow Windows blocking locks to be cancelled via a
CANCEL_LOCK call. TODO - restrict this to servers
that support NT_STATUS codes (Win9x will probably
not support this call).

Signed-off-by: Jeremy Allison <jra@samba.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>
(cherry picked from 570d4d2d895569825d0d017d4e76b51138f68864 commit)