LU-6881 update: add lock to protect commit check

LU-6881 update: add lock to protect commit check

In sub_trans_commit_cb(), the commit check should
be protected by lock, otherwise in some racy
scenarios, all committed will never be true,
even though all sub transaction has been committed.

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: I8f43ca8083753ab6eef4f2be56ef77bb8640bb79
Reviewed-on: http://review.whamcloud.com/15690
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Tested-by: Jenkins
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: James Simmons <uja.ornl@yahoo.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>