block/027: setup scsi_debug with MQ

block/027 focuses on race condition between blkg association and
request_queue shutdown. Unfortunately it is a bit easy to trigger
lockup by setting scsi_debug in the following way:

- single queue
- 21 LUNs
- small queue depth(110)
- 10us completion delay
- fio: 4 jobs, with iodepth 2048

The above setting creates big contention on tag allocation of blk-mq
code path, especially scsi_debug takes memcpy to simulate IO, which
doesn't match device in reality.

So setup scsi_debug with MQ and avoid to trigger lockup which doesn't
exist in real storage device usually.

Signed-off-by: Ming Lei <[email protected]>
Reviewed-by: Chaitanya Kulkarni <[email protected]>
[Shin'ichiro: fixed a shellcheck error]
Signed-off-by: Shin'ichiro Kawasaki <[email protected]>

tests/block/027

@@ -84,7 +84,7 @@ test() {
 	echo "Running ${TEST_NAME}"
 
 	scsi_debug_stress_remove virtual_gb=128 max_luns=21 ndelay=10000 \
-		max_queue=110
+		max_queue=110 submit_queues="$(nproc)"
 
 	echo "Test complete"
 }