add @propery to format method

the method is overided and need to be a property

Change-Id: Ica6eda8fa0161e4865182420caa5c59671328c58

vitrageclient/v1/cli/event.py

@@ -42,9 +42,6 @@ class EventPost(command.Command):
 
         return parser
 
-    def formatter_default(self):
-        return 'json'
-
     def take_action(self, parsed_args):
         if not parsed_args.type:
             raise exc.CommandException(

vitrageclient/v1/cli/rca.py

@@ -31,6 +31,7 @@ class RcaShow(show.ShowOne):
 
         return parser
 
+    @property
     def formatter_default(self):
         return 'json'
 

vitrageclient/v1/cli/topology.py

@@ -49,6 +49,7 @@ class TopologyShow(show.ShowOne):
 
         return parser
 
+    @property
     def formatter_default(self):
         return 'json'