osd: EC Optimizations fix peering bug causing unfound objects

osd: EC Optimizations fix peering bug causing unfound objects

Fix some unusual scenarios where peering was incorrectly
declaring that objects were missing on stray shards. When
proc_master_log rolls forward partial writes it need to
update pwlc exactly the same way as if the write had been
completed. This ensures that stray shards that were not
updated because of partial writes do not cause objects
to be incorrectly marked as missing.

The fix also means some code in GetMissing which was trying
to do a similar thing for shards that were acting,
recovering or backfilling (but not stray) can be deleted.

Signed-off-by: Bill Scales <bill_scales@uk.ibm.com>
(cherry picked from commit 83a9c0a9f8e9ed4f514adb32f1ae2df1602c3f88)