ctdb-daemon: Update logging for flag changes

ctdb-daemon: Update logging for flag changes

When flags change, promote the message to NOTICE level and switch the
message to the style that is currently generated by
ctdb-recoverd.c:monitor_handler().  This will allow monitor_handler()
to go away in future.

Drop logging when flags do not change.  The recovery master now logs
when it pushes flags for a node, so the lack of a corresponding
"changed flags" message here indicates that no update was required.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14784
Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>