[python] fix realtimeplotapp

realtimeplotapp calls Stop() on IvyMessagesInterface and expects it to only unbind.
Add an extra Shudown method for messagesapp that also stops Ivy.

sw/ground_segment/python/messages_app/messagesframe.py

@@ -139,5 +139,5 @@ class MessagesFrame(wx.Frame):
 
     def OnClose(self, event):
         self.timer.cancel()
-        self.interface.Stop()
+        self.interface.Shutdown()
         self.Destroy()

sw/lib/python/messages_tool.py

@@ -30,6 +30,9 @@ class IvyMessagesInterface():
 
     def Stop(self):
         IvyUnBindMsg(self.ivy_id)
+
+    def Shutdown(self):
+        self.Stop()
         IvyStop()
 
     def __init__del__(self):