Implement Service Validation

Service Validations aims to be used in all OpenStack modules to validate
that services are actually running.

Example in nova::api where we could validate the Nova API is really
working. If it's the case, a Puppet Anchor will be created. This Anchor
could be consummed by external tools to validate a deployment workflow
and improve the orchestration during an OpenStack deployment.

Change-Id: Ia74677b1402c8f872183f873cf9cb73702253874