ctdb-daemon: Add failover on shutdown

ctdb-daemon: Add failover on shutdown

Without this, NFS servers on other nodes will not go into grace before
this node releases locks.  This should also support improved behaviour
for SMB durable file handles.

The timeout is currently a constant 10s.  However, it will
subsequently be switched to an option.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15858

Signed-off-by: Martin Schwenke <mschwenke@ddn.com>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>