Release 1.8.0 only supports OpenStack Swift 1.8.0

Change-Id: I7e373c173d1953a75d4dabb17300a8af5a1f850a
Signed-off-by: Luis Pabon <lpabon@redhat.com>
Reviewed-on: http://review.gluster.org/5387
Reviewed-by: Peter Portante <pportant@redhat.com>