Clarify that the driver support library is interim
Clarify that the driver support library is interim

This patch is intended to clarify that Octavia is a service project
and not a library. It clarifies that the driver support callbacks are
temporary and will be removed in favor of a driver support endpoint.

Change-Id: Ic9dc596e86d414da1e8e20562f10ad490c51dbd9

openstack/octavia,openstack/octavia,openstack/octavia