scsi: scsi-mq: Wait for .queue_rq() if necessary

Ensure that if scsi-mq is enabled that scsi_internal_device_block()
waits until ongoing shost->hostt->queuecommand() calls have finished.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Cc: James Bottomley <jejb@linux.vnet.ibm.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Doug Ledford <dledford@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_lib.c

@@ -2893,7 +2893,7 @@ scsi_internal_device_block(struct scsi_device *sdev)
 	 * request queue. 
 	 */
 	if (q->mq_ops) {
-		blk_mq_stop_hw_queues(q);
+		blk_mq_quiesce_queue(q);
 	} else {
 		spin_lock_irqsave(q->queue_lock, flags);
 		blk_stop_queue(q);