Fix networking tree iscsi_tcp.c mis-merge

The removal of the 'waitqueue_active()' test in commit d7d05548
("[SCSI] iscsi_tcp: fix relogin/shutdown hang") got incorrectly resolved
by David when he back-merged the main git tree into the networking tree
in commit 278554bd ("Merge branch 'master' of master.kernel.org:...").

There was a content conflict due to 'sock->sk->sk_sleep' being changed
into 'sk_sleep(sock->sk)' in the networking tree, but David didn't pick
up the iscsi change from the main tree.

Reported-by: James Bottomley <James.Bottomley@suse.de>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>