message: Remove unnecessary ExchangeFaceNbrData() for pmesh in ex9p.
  The one for fes is necessary though.
diff: @@ -213,7 +213,6 @@ int main(int argc, char *argv[])
  {
  pmesh->UniformRefinement();
  }
  - pmesh->ExchangeFaceNbrData();
  // 7. Define the parallel discontinuous DG finite element space on the
  // parallel refined mesh of the given polynomial order.
  