ci: setup slurm on CI system for further tests

[adrianreber]

This adds an additional step to our existing CI scripts to run some of the tests from the test suite in GitHub's CI setup.

For now I am only running 5 tests to see if it works. So far it looks good.

I have to rebuild slurm to allow multiple slurmd processes on one host. This step could be skipped if we include the multihost support in our regular slurm build.