Remove neutron-vpnaas plugin from heat jobs
Remove neutron-vpnaas plugin from heat jobs

vpnaas is no longer part of neutron governace and openswan
(required for the reference implementation) package is not
available on ubuntu xenial.

We don't have any vpnaas integration tests in heat. So this
can be removed.

Change-Id: I7400d882c5d1e0efe49d49a982e82abdcdecdcfe

openstack-infra/project-config,openstack-infra/project-config,Tesora/tesora-project-config,Tesora/tesora-project-config