Make testdunefunctiongfs work in parallel again
For some reason, testdunefunctionsgfs segfaults in AMG when run in parallel. As the test isn't really about AMG, fix the problem by just using a simpler solver.
For some reason, testdunefunctionsgfs segfaults in AMG when run in parallel. As the test isn't really about AMG, fix the problem by just using a simpler solver.