Minor lbaasv2 things from the feature branch, needed in neutron

- Minor neutron.conf fix from feature branch until config is moved
- Some extra constants for extension
- Jinja template entry in services.conf

Change-Id: I4a15d0ac422457d2286d4b24d9f5067047e81563
Partially-Implements: blueprint services-split
Co-Authored-By: Brandon Logan <brandon.logan@rackspace.com>
Merge "Minor lbaasv2 things from the feature branch, needed in neutron"