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
Don't print duplicate messages on SystemExit

Don't log the error using LOG.error or LOG.exception and then
passing the same string to SystemExit since this will result in the
error being logged twice. Instead log the error and raise SystemExit(1).

Change-Id: I88b6632e6596a36a7168155dd4219e7d55078621
Merge "Don't print duplicate messages on SystemExit"
Merge "OVS and OF Agents: Create updated_ports attribute before setup_rpc"