This is immensely helpful to diagnose out-of-bounds accesses and memory
leaks.

- remove runtime by not executing unecessary runs
- make sure that on gp02 impi/2017 is NOT use
- adjust reserved time on knl systems

From now on call make check with TASKS=x, e.g.

make check TASKS=2

That way, this can easily be re-used for interactive testing as well