paxosservice: tolerate _active() call when not active
paxosservice: tolerate _active() call when not active

This can happen when multiple C_Active events are queued, and the first
does a propose_pending() (moving us into updating state).

Signed-off-by: Sage Weil <6dd34506bbd5e58221bbb3e4732d97c91f02277b@newdream.net>

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