osd: Optimized EC apply_pwlc needs to be careful about advancing last_complete

osd: Optimized EC apply_pwlc needs to be careful about advancing last_complete

Fix bug in apply_pwlc where the primary was advancing last_complete for a
shard doing async recorvery so that last_complete became equal to last_update
and it then thought that recovery had completed. It is only valid to advance
last_complete if it is equal to last_update.

Tidy up the logging in this function as consecutive calls to this function
often logged that it could advance on the 1st call and then that it could not
on the 2nd call. We only want one log message.

Signed-off-by: Bill Scales <bill_scales@uk.ibm.com>