Template show in cli should be by default in yaml

Templates are written as yaml so why not show them
in the cli by default as yaml. User can still see it
in json using the flag -f json

Change-Id: I17c5b26b8ef2a0ae02886dbf703c29434ad89781

vitrageclient/v1/cli/template.py

@@ -114,7 +114,7 @@ class TemplateShow(show.ShowOne):
 
     @property
     def formatter_default(self):
-        return 'json'
+        return 'yaml'
 
     def take_action(self, parsed_args):
         _id = parsed_args.id