Allow override of api interface bind address

We need to allow for kolla configs bind_host to be more configurable for kolla-kubernetes.

Problem description
===================

An IP configuration issue between kolla and kolla-kubernetes prevents
kolla containers from starting up in a Kubernetes environment. The core
of the problem is that host-targeted kolla configurations are
pre-generated, essentially hard-coding IP addresses within configuration
files. This works great for kolla, because one knows up front that a
particular kolla container is targeted to run on specific static hosts.
This will not work for kolla containers within the Kubernetes
environment, which must bind to random pod addresses, assigned
just-in-time, because pod/containers may be scheduled to run on any
machine, or even migrate from machine to machine, each time receiving a
new IP address on the overlay network as the pod/container moves around.