NVMe: Use a retryable error code on reset

BugLink: http://bugs.launchpad.net/bugs/1531539

A negative status has the "do not retry" bit set, which makes it not
retryable.  Use a fake status that can potentially be retried on reset.

An aborted command's status is overridden by the timeout handler so
that it won't be retried, which is necessary to keep initialization from
getting into a reset loop.
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
(cherry picked from commit 1d49c38c)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

drivers/nvme/host/pci.c

@@ -1017,7 +1017,7 @@ static void nvme_cancel_queue_ios(struct request *req, void *data, bool reserved
 	dev_warn(nvmeq->q_dmadev,
 		 "Cancelling I/O %d QID %d\n", req->tag, nvmeq->qid);
 
-	status = NVME_SC_CANCELLED;
+	status = NVME_SC_ABORT_REQ;
 	if (blk_queue_dying(req->q))
 		status |= NVME_SC_DNR;
 	blk_mq_complete_request(req, status);