VOL-3121 -  Separated out logical ports from logical agent.

Similar to flows/groups/meters.
Also modified device_route tests to generate unique port IDs (`.OfpPort.PortNo`s) across all UNI ports withing each test, i.e. within an OLT.
Also replaced logicalPortsNo map & associated NNI vs UNI logic with root device checks.

Change-Id: Ib0cecbf7d4f8d509ce7c989b9ccf697c8b0d17d6
diff --git a/rw_core/core/device/agent_flow.go b/rw_core/core/device/agent_flow.go
index bb8fe08..58f9aa9 100644
--- a/rw_core/core/device/agent_flow.go
+++ b/rw_core/core/device/agent_flow.go
@@ -22,7 +22,7 @@
 
 // listDeviceFlows returns device flows
 func (agent *Agent) listDeviceFlows() map[uint64]*ofp.OfpFlowStats {
-	flowIDs := agent.flowLoader.List()
+	flowIDs := agent.flowLoader.ListIDs()
 	flows := make(map[uint64]*ofp.OfpFlowStats, len(flowIDs))
 	for flowID := range flowIDs {
 		if flowHandle, have := agent.flowLoader.Lock(flowID); have {