osd/PG: MissingLoc: track location counts by upset and other

osd/PG: MissingLoc: track location counts by upset and other

For every object in missing_loc, calculate how many known locations are in
the upset and all others, and call that loc_count_t.  Keep
a map of loc_count_t to the number of missing objects with that
distribution.

Signed-off-by: Sage Weil <sage@redhat.com>
Signed-off-by: David Zafman <dzafman@redhat.com>
(cherry picked from commit eddf510e734b8bdded271350c0b00428669559ff)

Conflicts:
	src/osd/PG.cc : Resolved in add_batch_sources_info, check_recovery_sources
	src/osd/PrimaryLogPG.cc : Deleted check_recovery_sources