[SCSI] iscsi bugfixes: send correct error values to userspace

In the xmit patch we are sending a -EXXX value to iscsi_conn_failure
which is causing userspace to get confused.

We should be sending a ISCSI_ERR_* value that userspace understands.

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