[PATCH] nvme-pci: drain the entered requests after ctrl is shutdown

[Sagi Grimberg]

> Currently, we will unquiesce the queues after the controller is
> shutdown to avoid residual requests to be stuck. In fact, we can
> do it more cleanly, just wait freeze and drain the queue in
> nvme_dev_disable and finally leave the queues quiesced.

Does this fix a bug? What is the benefit of leaving the queues
quiesced in shutdown?