open gre in addition to vxlan

This patch teaches quickstack::neutron about GRE.  It opens GRE access
anywhere that vxlan access was already permitted.

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=1072325

True, but that is more likely an oversight than intentional.  I believe all the firewall modules we have in quickstack::firewall have the include.  We can fix this later if needed, but I just thought we should be safe and have all new firewall chunks invoke that include to make sure things were set up that we expect to be there.