Propagate port change to SDN controller via OF13

This change adds plumbing to propagate new logical port
additions up to the SDN contoller via OpenFlow.

Change-Id: Ic02586b096144c3697a0974ebbc8a7be8760bef8
diff --git a/ofagent/connection_mgr.py b/ofagent/connection_mgr.py
index 8d25891..1aa7031 100644
--- a/ofagent/connection_mgr.py
+++ b/ofagent/connection_mgr.py
@@ -209,3 +209,9 @@
         if datapath_id:
             agent = self.agent_map[datapath_id]
             agent.forward_packet_in(ofp_packet_in)
+
+    def forward_change_event(self, device_id, event):
+        datapath_id = self.device_id_to_datapath_id_map.get(device_id, None)
+        if datapath_id:
+            agent = self.agent_map[datapath_id]
+            agent.forward_change_event(event)