Fake event: use low level radical address fix

tracim/tracim/lib/calendar.py

         if not low_level:
             return cfg.RADICALE_CLIENT_BASE_URL_TEMPLATE
 
-        return '127.0.0.1:{0}'.format(cfg.RADICALE_SERVER_PORT)
+        return 'http://127.0.0.1:{0}'.format(cfg.RADICALE_SERVER_PORT)
 
     @classmethod
     def get_user_base_url(cls):