This allows ironic service endpoints to use custom hostnames, and adds the
following variables:

* ironic_internal_fqdn
* ironic_external_fqdn
* ironic_inspector_internal_fqdn
* ironic_inspector_external_fqdn

These default to the old values of kolla_internal_fqdn or
kolla_external_fqdn.

This also adds ironic_api_listen_port and ironic_inspector_listen_port
options, which default to ironic_api_port and ironic_inspector_port for
backward compatibility.

These options allow the user to differentiate between the port the
service listens on, and the port the service is reachable on. This is
useful for external load balancers which live on the same host as the
service itself.

Change-Id: I45b175e85866b4cfecad8451b202a5a27f888a84
Implements: blueprint service-hostnames