LU-6527 ldiskfs: Journal commit callback optimization

LU-6527 ldiskfs: Journal commit callback optimization

Porting patch for RHEL7, SLES11 & SLES12

This is a porting patch from:
Lustre-change: http://review.whamcloud.com/14611/
Lustre-commit: 55afbf5934e145e48a31193de601abd58e605a42

    Don't take spinlock in tgt_cb_last_committed, if
    exp_last_committed was updated with higher trasno.
    Also change list_add_tail to list_add. It gives
    advantages to ldiskfs in tgt_cb_last_committed.
    In the beginning of list will be placed thandles
    with the highest transaction numbers. So at the
    first iterations we will have the highest transno.
    It will save from extra call of
    ptlrpc_commit_replies.

Signed-off-by: Sergey Cheremencev <sergey.cheremencev@seagate.com>
Xyratex-bug-id: MRP-2575
Reviewed-by: Alexander Zarochentsev <alexander.zarochentsev@seagate.com>
Reviewed-by: Alexander Boyko <alexander.boyko@seagate.com>
Tested-by: Alexander Lezhoev <alexander.lezhoev@seagate.com>
Reviewed-by: Alexey Leonidovich Lyashkov <alexey.lyashkov@seagate.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Mike Pershin <mike.pershin@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: Yang Sheng <yang.sheng@intel.com>
Change-Id: I3e7f28e5386cf77f3139ff0d330afadf8864c293
Reviewed-on: http://review.whamcloud.com/18835
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>