Docs should tell users about LBaaS v2 differences

[Major Hayden]

Liberty has LBaaS v2 (octavia) available and we have good documentation on the topic:

http://docs.openstack.org/developer/openstack-ansible/install-guide/configure-lbaas.html

However, we should mention to users that:

* LBaaS v2 isn't visible in Horizon in Liberty[1]
* LBaaS v2 uses the lbaas-* arguments for neutron's CLI client, not lb-*

This should reduce confusion, especially for newer deployers.

[1] http://docs.openstack.org/admin-guide-cloud/networking_config-agents.html#configure-load-balancer-as-a-service-lbaas

[Major Hayden (rackerhacker)]

This patch should be in liberty for sure, but I'm not sure if Mitaka has LBaaS v2 panels in Horizon yet.

[Major Hayden (rackerhacker)]

LBaaS v2 panels are planned for Mitaka's Horizon: https://mitakadesignsummit.sched.org/event/49y4/load-balancing-as-a-service-liberty-and-beyond

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/272198

[OpenStack Infra (hudson-openstack)]

Change abandoned by Major Hayden (<email address hidden>) on branch: master
Review: https://review.openstack.org/272198
Reason: We're missing lbaasv2 in Mitaka/Liberty.

[Major Hayden (rackerhacker)]

We're missing the LBaaSv2 API altogether in mitaka/liberty. I'll make a separate bug for that.