blk-mq: stop hardware queue in blk_mq_delay_queue()

The run handler we register for the delayed work requires that the
queue be stopped, yet we leave that up to the caller. Let's move
it into blk_mq_delay_queue() itself, so that the API is sane.

This fixes a stall with SCSI, where it calls blk_mq_delay_queue()
without having stopped the queue. Hence the queue is never run.
Reported-by: Hannes Reinecke <hare@suse.com>
Fixes: 70f4db63 ("blk-mq: add blk_mq_delay_queue")
Signed-off-by: Jens Axboe <axboe@fb.com>

block/blk-mq.c

@@ -1170,6 +1170,7 @@ void blk_mq_delay_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs)
 	if (unlikely(!blk_mq_hw_queue_mapped(hctx)))
 		return;
 
+	blk_mq_stop_hw_queue(hctx);
 	kblockd_schedule_delayed_work_on(blk_mq_hctx_next_cpu(hctx),
 			&hctx->delay_work, msecs_to_jiffies(msecs));
 }