message: When derefining a mesh in parallel preserve the global
  attribute lists.
  Currently, the global attribute lists are replaced with
  the local lists.
diff: @@ -6077,6 +6077,10 @@ void Mesh::DerefineMesh(const Array<int> &derefinements)
  Mesh* mesh2 = new Mesh(*ncmesh);
  ncmesh->OnMeshUpdated(mesh2);
  + // In parallel, preserve the global attribute lists.
  + attributes.Copy(mesh2->attributes);
  + bdr_attributes.Copy(mesh2->bdr_attributes);
  +
  Swap(*mesh2, false);
  delete mesh2;
  