It triggered the queue authentication work elements in parallel, but
the ctrl authentication work itself completes when all of them
completes. Hence wait for queues auth completions.

This also makes nvme_auth_stop simply a sync cancel of ctrl
dhchap_auth_work.
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>