mon: do not stop mds0 unless all other nodes have also stopped
mon: do not stop mds0 unless all other nodes have also stopped

If we are the root node or the tableserver, we have to shut down last.
(And even then, if we have client sessions, we can't fully shut down, we
can only kill ourselves!)

Fixes: #1048 (sorta)
Signed-off-by: Sage Weil <c5b6ff1fd4f0bde10db63d7a3e07166cf6c4229f@dreamhost.com>

ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph,ajnelson/ceph