osd: add osd_fast_shutdown_notify_mon option (default false)

osd: add osd_fast_shutdown_notify_mon option (default false)

The osd_fast_shutdown option may cause the cluster log to receive
too many entries of 'osd.X reported immediately failed by osd.Y',
depending on cluster scale.

This might be an issue for LMA stacks/tools that check ceph logs
for failed lines, and then require additional logic to filter on
an intended OSD (fast) shutdown; might not be an option/possible,
and require an admin to analyze.

So, add osd_fast_shutdown_notify_mon option for OSD to also tell
the monitor it is shutting down (done in slow/non-fast shutdown)
under osd_fast_shutdown.

This introduces minimal delay (the ack from the mon is required
to prevent the messages), and addresses the cluster log issue.
Note: the osd_mon_shutdown_timeout option can be used to control
the maximum amount of time waiting for the monitor ack to arrive.

Fixes: http://tracker.ceph.com/issues/46978
Signed-off-by: Mauricio Faria de Oliveira <mfo@canonical.com>
(cherry picked from commit c75734729764868c5c501722fc8de08dac9ebd4a)