Ensure designate-sink has policy initialized

We split the designate Service class into a base Service class,
and a RPCService class.

Service contains code common to every Designate service, while
RPCService contains code for any RPC servers.

Closes-Bug: 1366764
Change-Id: I2410a83c9f4123b2011f4f6409aacb18f010097f
Merge "Ensure designate-sink has policy initialized"