Ensure keystone endpoint set before service starts

This patch ensures that in the case where keystone and
nova-api are on the same node, nova-api is not started
until the keystone catalog contains the compute service
and endpoint required to use nova.

Change-Id: Ia49874a01582802ba457c9117747aeff203590c3
Merge git://github.com/puppetlabs/puppetlabs-nova