Avoid saving and setting refinement flags in distributed Tria

[kronbichler]

I noticed that the lines

dealii/source/distributed/tria.cc

Lines 2749 to 2753 in f262a26

	this->dealii::Triangulation<dim, spacedim>::
	prepare_coarsening_and_refinement();
	this->update_periodic_face_map();
	// enforce 2:1 mesh balance over periodic boundaries
	mesh_changed = enforce_mesh_balance_over_periodic_boundaries(*this);

already report any change we could make in this function, so rather than saving the flags again (which incurs a non-negligible cost), I decided to pick up that information.