Current status:
* the agent supports cummunication with the server via oslo.messaging
* the agent implements RPC interface required by
https://review.openstack.org/#/c/71015/
The interface and implementation is defined in
savanna.guestagent.AgentEndpoint
Implements: blueprint guest-agent
Change-Id: I88cf5bb4c49b22293b0b299f182f55a4d179c877