iscsi.py: cleanup - remove temp variable

Don't need to assign new variable to use target.iqn

Change-Id: Ieb581010fab9f56de22c34b67b91b88f8ca3612f
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/25710
Reviewed-by: Dan Kenigsberg <danken@redhat.com>