ctdb-recovery: Factor out new function set_recmode_handler()

ctdb-recovery: Factor out new function set_recmode_handler()

This is used to reply to the recmode control for all the different
cases.  The callers can later be generalised to use a pointer, which
can then be used for recovery lock handling in different contexts.

Note that the handle is now freed in set_recmode_handler() rather than
the callbacks.

There is one difference in behaviour.  Deferred attach calls are now
processed in the timeout case, where they weren't before.  That's a
bug fix!

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>