[gridcreator] solve FS#267

This solves FS#267:
http://www.dumux.org/flyspray/index.php?do=details&task_id=267&project=3

The solution is to define the static variables inside static functions.
Then they will be destroyed on time, i.e., before MPI_Finalize is
called.

Reviewed by gruenich.



git-svn-id: svn://svn.iws.uni-stuttgart.de/DUMUX/dumux/trunk@15043 2fb0f335-1f38-0410-981e-8018bf24f1b0