lockd: unregister notifier blocks if the service fails to come up completely

If the lockd service fails to start up then we need to be sure that the
notifier blocks are not registered, otherwise a subsequent start of the
service could cause the same notifier to be registered twice, leading to
soft lockups.

Signed-off-by: Scott Mayhew <smayhew@redhat.com>
Cc: stable@vger.kernel.org
Fixes: 0751ddf7 "lockd: Register callbacks on the inetaddr_chain..."
Signed-off-by: J. Bruce Fields <bfields@redhat.com>