Improvements to auto repair
------------------------
We should allow auto repair for bluestore pools since it has built in
checksums. Currently, we are limited to erasure coded pools.
In order to trigger a auto repair when regular scrub detects errors,
any errors should immediately schedule a deep-scrub.
Add a new pg state flag "failed_repair" when repairs can't fix all
errors. This may be tricky to implement because pg repair ends as a
recovery operation.
Set failed_repair if primary repair triggered by a client read fails.
Add a count of number of objects that are repaired to PG stats and OSD
stats.
David
