mgr: adjust DaemonState device index when daemon metadata is updated

mgr: adjust DaemonState device index when daemon metadata is updated

We need to unregister the old metadata (in particular, its devices
in the DaemonState device indexes) before adjusting and reregistering
the new metadata.

Do the whole thing under the DaemonState lock to that there isn't a window
where the osd metadata isn't present at all.

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