message: fix bug where transfer function updates did not work w/ mpi-offload
diff: #include <imgui.h>
  #include "TransferFunctionWidget.h"
  -
  +// job_scheduler
  #include "../../jobs/JobScheduler.h"
  -
  +// sg_ui
  #include "../sg_ui/ospray_sg_ui.h"
  +// ospray_sg
  +#include "ospray/sg/visitor/MarkAllAsModified.h"
  using namespace tfn;
  using namespace tfn_widget;
  @@ -166,10 +168,9 @@ TransferFunctionWidget::TransferFunctionWidget(
  tfn->add(colors);
  tfn->add(alphas);
  - colors->markAsModified();
  - alphas->markAsModified();
  -
  tfn->updateChildDataValues();
  +
  + tfn->traverse(sg::MarkAllAsModified{});
  });
  };
  