LU-4403 mds: extra lock during resend lock lookup.

LU-4403 mds: extra lock during resend lock lookup.

1. If the request does not require open lock, MDT does not
need to search the lock in exp_hash_lock list, because the MDT
will release the lock anyway, and it can always re-enqueue the
request during resend.

2. Lock the resource when the MDS is trying to lookup the lock for
resend request(in mdt_intent_fixup_resent). Otherwise, if the
lock is being released, fixup_resent will return a released lock,
which will cause LBUG when this lock is being released later.

Lustre-change: http://review.whamcloud.com/#/c/8680/
Lustre-commit: 96dba12553f1fab5344f5eb7346181bee8e1ea59

Change-Id: Ie106ca46b2b390d178b454655cda54c702cc244e
Signed-off-by: wang di <di.wang@intel.com>
Reviewed-on: http://review.whamcloud.com/9779
Tested-by: Jenkins
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: John L. Hammond <john.hammond@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>