nvme-auth: do not re-authenticate queues with no prior authentication

When sending 'connect' the queues can figure out from the return code
whether authentication is required or not. But reauthentication doesn't
disconnect the queues, so this check is not available.  Rather we need
to check whether the queue had been authenticated initially to figure
out if we need to reauthenticate.

Signed-off-by: Hannes Reinecke <hare@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>