mon: fix recent paxos sync from 0 when first_committed == 1

This is okay; allow it.

Signed-off-by: Sage Weil <sage@inktank.com>
mon: fix off-by-one: no need to reapply previous last_committed after sync

The old last_committed is already committed; don't reapply. This also fixes
the case where lc was 0 (i.e., we did get_cookie_recent from the beginning
of time).

Signed-off-by: Sage Weil <sage@inktank.com>
mon: fix sync_start doc

Signed-off-by: Sage Weil <sage@inktank.com>
mon: factor out stashing latest monmap, lc lower bound

Signed-off-by: Sage Weil <sage@inktank.com>
mon: stash latest state when flagging force_sync

Store our latest state when we set the force_sync flag.  This is important
because we will clear the store the next time we start up and may not be
able to get a useful monmap at that point.

Signed-off-by: Sage Weil <sage@inktank.com>
mon: clean up check_fsid() a bit

Use the uuid_d type instead of kludging string comparisons.

Signed-off-by: Sage Weil <sage@inktank.com>