[VOL-2697] Avoid key error for vlan_vid_mask during flow stats reply

Change-Id: I9f55726fa70918bb1b00ff874531ac75ee571238
diff --git a/ofagent/of_connection.py b/ofagent/of_connection.py
index 8930472..a941111 100755
--- a/ofagent/of_connection.py
+++ b/ofagent/of_connection.py
@@ -98,7 +98,7 @@
         :return: None
         """
         assert self.connected
-        
+
         if msg.xid is None:
             msg.xid = self._gen_xid()
         buf = msg.pack()