Renders GrrMessage payload and renames args_rdf_name field.

def RenderPayload(self, result, value):
    """Renders GrrMessage payload and renames args_rdf_name field."""
    if "args_rdf_name" in result:
      result["payload_type"] = result["args_rdf_name"]
      del result["args_rdf_name"]

    if "args" in result:
      result["payload"] = self._PassThrough(value.payload)
      del result["args"]

    return result