Add LBaaS Support

We now have a couple of parties interested in Neutron's LBaaS feature. To enable this option, we need to do a couple of things:

First, we need to enable the LBaaS agent in Neutron. There's already a manifest for this in our puppet-neutron module, so this should be pretty easy...it probably boils down to adding:

  - "%{network_service}::agents::lbaas"

to data/class_groups/network_controller.yaml. Next, we'd need to ensure that Horizon gets a corresponding config:

https://github.com/stackforge/puppet-horizon/blob/stable/havana/templates/local_settings.py.erb#L176

Third, we probably need to pull in some updates to stackforge's stable/havana branch which deal with some dependency issues.