Ceph

If a PG is in the process of getting removed and we repeer and discover we want to keep it, we currently block waiting for the removal to complete. This isn't very difficult to trigger by starting a rebalance (ceph osd out N) and then switching back (ceph osd in N).

Instead, we should resurrect the existing PG content.

Moving it completely out of the way is tricky because of leveldb. And in any case, resurrection is "ideal".