GlobalTestConfig: Solver override does not work if Gurobi is not installed

[maxkratz]

If GLPK is not installed on the system running the tests, the solver override functionality in GlobalTestConfig.java does not work. All tests will fail because the GIPS API can not be properly initiated if GLPK is not installed (if GLPK is the chosen solver in the respective GIPSL files).

[maxkratz]

Update: Since we now use Gurobi as the default ILP solver, I changed the title of this issue.

[maxkratz]

After merging this PR (Echtzeitsysteme/gips#229), this "bug" may be solved already.

[maxkratz]

After merging this PR (Echtzeitsysteme/gips#229), this "bug" may be solved already.

Yes, I could not reproduce it anymore with the latest release of the GIPS VM.