[SCSI] iscsi_tcp: fix fd leak

This patch should fix the file descriptor leak problem. A quick look
through the kernel shows that users of sockfd_lookup use sockfd_put to
release their handle. We were using sock_release which from the comments
and code look like it does not release the get() on the file from the
lookup.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>