NSXV3 is the OpenStack support for the NSX Transformers platform.
This is supported from neutron in the Mitaka version. This patch
adds Kolla support

This adds a new neutron_plugin_agent type 'vmware_nsxv3'. The plugin
does not run any neutron agents.

Change-Id: I1ecd7e5f3471e4ff03cfe8c9a3aff17af3fe1842