fix wrong replies for change and do

now correctly reply with 'changed' and 'done'

Change-Id: Ic2b8e6d6d7d4c8301dc8b273115a10e1f8e40a2e

secop/protocol/messages.py

@@ -103,7 +103,7 @@ class CommandRequest(Message):
 class CommandReply(Message):
     is_reply = True
     command = ''
-    arguments = None
+    result = None
 
 class WriteRequest(Message):
     is_request = True