osd: persist inconsistent objs using omap

osd: persist inconsistent objs using omap

persist inconsistent objects found when comparing the ScrubMaps
collected from replica/shards. the discrepancies between the auth
copy and the replica are identified as inconsistencies. and hence
encoded into the omap of an object of the temp coll of the PG in
question.
scrub_types.{h,cpp} are introduced to hide the details of how we
persist the scrub types from the librados client.

Signed-off-by: Kefu Chai <kchai@redhat.com>