osd: fix recovery requeue race
osd: fix recovery requeue race

If a recovery op finished right as another recovery op was
begin started, we could get into start_recovery_ops() and get
max = 0 and not start anything.  Since the PG wasn't being
requeued for later, it would never recover.  So, requeue if we
race and get max == 0.

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