message: define data_layout as unknown for pack
diff: @@ -2541,6 +2541,8 @@ void TFImporter::parsePack(tensorflow::GraphDef& net, const tensorflow::NodeDef&
  if (dim != 0)
  CV_Error(Error::StsNotImplemented, "Unsupported mode of pack operation.");
  + data_layouts[name] = DATA_LAYOUT_UNKNOWN;
  +
  CV_Assert(hasLayerAttr(layer, "N"));
  int num = (int)getLayerAttr(layer, "N").i();
  CV_CheckEQ(num_inputs, num, "");
  