Adapt to the distributed trust-region solver

Currently, that solver requires the function space basis to be
defined on a level(!) grid view.

src/quasiconvexity-test.cc

@@ -119,8 +119,13 @@ int main (int argc, char *argv[]) try
   if (mpiHelper.rank()==0)
     std::cout << "There are " << grid->leafGridView().comm().size() << " processes" << std::endl;
 
+#if HAVE_DUNE_PARMG
+  typedef GridType::LevelGridView GridView;
+  GridView gridView = grid->levelGridView(0);
+#else
   typedef GridType::LeafGridView GridView;
   GridView gridView = grid->leafGridView();
+#endif
 
   // FE basis spanning the FE space that we are working in
   typedef Dune::Functions::LagrangeBasis<GridView, order> FEBasis;