Fix different behavior in python3.4 json module

THe 3.4 json changes the way json.dumps works when indent is specified,
which breaks tests. Passing the separators argument explicitely forces
the old behavior back.

Change-Id: Ie27eb1491b984e65fedeb21864e2833ada2872fe

heatclient/common/utils.py

@@ -49,7 +49,8 @@ def link_formatter(links):
 
 
 def json_formatter(js):
-    return jsonutils.dumps(js, indent=2, ensure_ascii=False)
+    return jsonutils.dumps(js, indent=2, ensure_ascii=False,
+                           separators=(', ', ': '))
 
 
 def text_wrap_formatter(d):