LU-3618 ptlrpc: rq_commit_cb is called for twice

LU-3618 ptlrpc: rq_commit_cb is called for twice

If a ptlrpc_request is already on imp::imp_replay_list, when it's
replayed and replied, after_reply() will call req::rq_commit_cb
for the request, then call it again in ptlrpc_free_committed.

Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Change-Id: I796c3351ad896aa3e1d0c2147ca7f775b7c14bfc
Reviewed-on: http://review.whamcloud.com/8815
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>