iscsi-target: Drop duplicate __iscsi_target_login_thread check

This patch drops the now duplicate + unnecessary check for -ENODEV from
iscsi_transport->iscsit_accept_np() for jumping to out:, or immediately
returning 1 in __iscsi_target_login_thread() code.

Since commit 81a9c5e7 the jump to out: and returning 1 have the same
effect, and end up hitting the ISCSI_NP_THREAD_SHUTDOWN check regardless
at the top of __iscsi_target_login_thread() during next loop iteration.

So that said, it's safe to go ahead and remove this duplicate check.

Reported-by: Joern Engel <joern@logfs.org>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>