pass the MPI communicator to the DGF grid loader

this fixes the parallel stuff for problems which load their grids from
a DGF file. The problems which use other grid creators (e.g. the 2pni
test problem) seem to not need this...

git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@7988 2fb0f335-1f38-0410-981e-8018bf24f1b0

dumux/common/dgfgridcreator.hh

@@ -27,6 +27,7 @@
 #define DUMUX_DGF_GRID_CREATOR_HH
 
 #include <dune/grid/io/file/dgfparser.hh>
+#include <dune/common/mpihelper.hh>
 
 #include <dumux/common/propertysystem.hh>
 #include <dumux/common/parameters.hh>
@@ -55,7 +56,7 @@ public:
     {
         const std::string dgfFileName = GET_RUNTIME_PARAM(TypeTag, std::string, gridFile);
 
-        gridPtr_ = GridPointer(dgfFileName.c_str());
+        gridPtr_ = GridPointer(dgfFileName.c_str(), Dune::MPIHelper::getCommunicator());
     };
 
     /*!