Fix undefined NeutronCorePluginML2Ansible
Fix undefined NeutronCorePluginML2Ansible

This is partial revert of f90f685d5d22b12f3d74a141ce57d9cee02e0047 and
makes sure the  NeutronCorePluginML2Ansible service resource is defined
because it is still referenced to enable networking-ansible which is
now deprecated.

Closes-Bug: #1980202
Change-Id: I01d652094db921a8273f630fbe07f0535c1e8452

openstack/tripleo-heat-templates,openstack/tripleo-heat-templates