osd/scrub: auto-correct accounting-only stat mismatches

osd/scrub: auto-correct accounting-only stat mismatches

When scrub detects a PG stats mismatch but no object-level
inconsistencies (all replicas agree on actual data), fix the
stats in place rather than reporting a scrub error.

Previously, a pure stat mismatch would log [ERR], increment
shallow_errors, and trigger OSD_SCRUB_ERRORS / PG_STATE_INCONSISTENT
health alerts — yet leave the stats unfixed unless a repair
scrub was manually initiated. The scrubber's own object count
is authoritative in this case.

Persistence of the corrected stats is deferred until the next
transaction that sets dirty_info, consistent with the existing
stats_invalid repair path.

Signed-off-by: Ronen Friedman <rfriedma@redhat.com>