osd: Optimized EC add_log_entry should not skip partial writes

osd: Optimized EC add_log_entry should not skip partial writes

Undo a previous attempt at a fix that made add_log_entry skip adding partial
writes to the log if the write did not update this shard. The only case where
this code path executed is when a partial write was to an object that needs
backfilling or async recovery. For async recovery we need to keep the
log entry because it is needed to update the missing list. For backfill it
doesn't harm to keep the log entry.

Signed-off-by: Bill Scales <bill_scales@uk.ibm.com>
(cherry picked from commit 9f0e883b710a06e3371bc7e0681e034727447f27)