Wire Neutron ML2 plugin and OVS agent settings as arrays

Wire Neutron ML2 plugin and OVS agent settings as arrays

Wires the following as arrays to the neutron module:
 - mechanism_drivers
 - flat_networks
 - tenant_network_types
 - tunnel_types
 - bridge_mappings

Also updates the template version to use a Liberty feature which
allows serialization of comma_delimited_list into JSON.

Tidies up the manifests by removing the class declarations since
config is passed by the puppet/controller+compute hiera mapped_data.

Change-Id: Ie9f85fb827099f897ef750e267bc3ed3a864fe59
Co-Authored-By: Steven Hardy <shardy@redhat.com>