OVS and OF Agents: Create updated_ports attribute before setup_rpc

setup_rpc spawns rpc-consuming thread that can access
self.updated_ports before it is created in the constructor

Change-Id: Icc447c3bb7099125aae30e2430a6ad98ba00f6f9
Closes-Bug: #1314472
Merge "OVS and OF Agents: Create updated_ports attribute before setup_rpc"