LU-9197 llog: return 0 if llog destroy fails

LU-9197 llog: return 0 if llog destroy fails

In llog_cancel_rec(), let's return 0 if only destroying the
final plain llog fails, because the bitmap has been cleared
successfully, and the orphan supposed to be handled by LFSCK
anyway. So let's not try to destroy again, which will pretty
much complicate the code here.

And also in this case, we do not need restore the llh_count and
bitmap, because the record has been deleted for llog anyway.

Signed-off-by: Di Wang <di.wang@intel.com>
Change-Id: I762def0f0de08a2960997ab9463f4e72fbad531d
Reviewed-on: https://review.whamcloud.com/26069
Tested-by: Jenkins
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>