Only one entry created for nova-osapi_compute and nova-metadata services in multi-n-api environment

Description
===========

In nova.conf, osapi_compute_listen and metadata_listen are defaulted to 0.0.0.0. Due to this when multiple n-api nodes are setup in a multinode environment, only one entry is
created for nova-osapi_compute and nova-metadata services in nova.services table.

This doesn't have any effect when n-api's on both nodes have same version. But when n-api on node 1 is upgraded, then n-api on node2 refuses to start due to Service version too Old exception.
This behavior can be changed by having two entries for these services in db.

Steps to reproduce
==================

1. Setup multinode devstack environment with all controller services on one node and n-api & n-cpu on another node.
2. Now you have two n-api nodes.
3. Check nova.services table.

Expected result
===============

There should be two entries for nova-osapi_compute and nova-metadata services in nova.services table one for each host.

Actual result
=============

Only one entry created for these services.