[SCSI] cxgb3i: Fix a login over vlan issue

Fix a target login issue, when parent interface is vlan and we are
using cxgb3i sepecific private ip address in '/etc/iscsi/ifaces/'
iface file.

Signed-off-by: Rakesh Ranjan <rakesh@chelsio.com>
Acked-by: Karen Xie <kxie@chelsio.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>