LU-2275 mdc: Don't leak requests with "strange" dispositions

LU-2275 mdc: Don't leak requests with "strange" dispositions

Make sure that a request with no transno will get its rq_replay reset,
also ensure that on error path from ll_file_open we drop reference to
request occupied by open if needed.

Change-Id: If4d59274d2574698567970821b94ef1c5c35385b
Signed-off-by: Oleg Drokin <green@whamcloud.com>
Reviewed-on: http://review.whamcloud.com/4458
Reviewed-by: Peng Tao <bergwolf@gmail.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Fan Yong <yong.fan@whamcloud.com>