Avoid that nvme_queue_rq() is still running when nvme_stop_queues()
returns. Untested.

Signed-off-by: Bart Van Assche <redacted>
Cc: Keith Busch <redacted>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Sagi Grimberg <sagi@grimberg.me>

Bart this looks really good! and possibly fixes an issue
I've been chasing with fabrics a while ago. I'll take it
for testing but you can add my:

Reviewed-by: Sagi Grimberg <sagi@grimberg.me>