images: Build debian-iptables:stretch-v1.2.0
images: Build debian-iptables:stretch-v1.2.0

- Removes iptables-wrapper, which was extraneous for the stretch
  variant of this image

Signed-off-by: Stephen Augustus <f96984fef9637085f0559f1484dfd4e99545cd6e@vmware.com>

kubernetes/release,kubernetes/release