Clean now also means the correct number of replicas, whereas recovered
means we have done all the work we can do given the replicas/osds we have.
For example, degraded and clean are now mutually exclusive.
Also move away from 'till'.
If we backfill, we fail to peer instead of having every object show up as
'unfound'. Avoid that by preventing log trimming, so that we always do
log recovery for this test.
