Trove/populate-remote-from-keystone-catalog

Description
This change is to use the keystone service catalog to populate the endpoint URLs for the nova, swift, heat and cinder clients.

Justification/Benefits
By obtaining the URL from the keystone catalog, we dont have to keep these URLs in the config. Another benefit is if the endpoints change, trove will obtain the new endpoints for these clients without having to change the configuration and restart.

Configuration
The following configuration keys will be deleted: nova_compute_url, cinder_url, swift_url and heat_url. These URLs will be populated from keystone service catalog

Database
No schema change is required.

Public API
No change in API

CLI interface
No change in CLI

Internal API
No change in internal API

Guest Agent
No changed in the guestagent code. The only change is that the endpoint URLs will be removed from the trove-guestagent.conf