nvmet-fc: abort command when there is no binding

When the target port has not active port binding, there is no point in
trying to process the command as it has to fail anyway. Instead adding
checks to all commands abort the command early.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>