Avoid clobbering existing tests for SuperLU

We inherited this test from the Dune repositories, but failed to install sufficient protection in the form of symbol renaming to guarantee that both tests could coexist.

This issue was exposed by a recent pull request in the OPM-Porsol repository, namely OPM/opm-porsol#16.

While we are in the process of transitioning to CMake-based builds, it is nevertheless prudent to not cause errors for would-be consumers of OPM-Core