ctdb-recoverd: Store recovery lock handle

ctdb-recoverd: Store recovery lock handle

... not just cluster mutex handle.

This makes the recovery lock handle long-lived and with allow the
releasing code to cancel an in-progress attempt to take the recovery
lock.

The cluster mutex handle is now allocated off the recovery lock
handle.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13617

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>
(cherry picked from commit c52216740bd81b68876de06e104822bbbca86df9)