Fixed two bugs in OpenFlow land

Change-Id: I74f37221d93c71398a1985143f03706297bd1661
diff --git a/ofagent/grpc_client.py b/ofagent/grpc_client.py
index a17d104..69bf940 100644
--- a/ofagent/grpc_client.py
+++ b/ofagent/grpc_client.py
@@ -78,7 +78,7 @@
         returnValue(res.items)
 
     @inlineCallbacks
-    def list_group(self, datapath_id):
+    def list_groups(self, datapath_id):
         device_id = self.device_id_map[datapath_id]
         req = ID(id=device_id)
         res = yield threads.deferToThread(