Remote Designate Agent Calls Fail

Fix the Agent RPC API methods and method signatures to align properly with the method signatures of the backend drivers.
Fix the RPC backend driver methods and method signatures to align properly with the other backend drivers.

Change-Id: I284c1a5f6dd1f1acf5165799c7103b8b86edbd35
Closes-bug: #1272332
Merge "Remote Designate Agent Calls Fail"