LU-8097 mdt: remove assertion for lock resent

LU-8097 mdt: remove assertion for lock resent

Do not assert for missing lock for resent, because the lock
might be destroyed by other thread in the mean time.

Signed-off-by: Di Wang <di.wang@intel.com>
Change-Id: If184684ec734e7162e570d3044d9ece5f3ac3567
Reviewed-on: http://review.whamcloud.com/19974
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>