nvmet-fcloop: Remove remote port from list when unlinking

The remote port is removed too late from fcloop_nports list. Remove it
when port is unregistered.

This prevents a busy loop in fcloop_exit, because it is possible the
remote port is found in the list and thus we will never progress.

The kernel log will be spammed with

  nvme_fcloop: fcloop_exit: Failed deleting remote port
  nvme_fcloop: fcloop_exit: Failed deleting target port

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