fix: Parallel Jenkins stages

[itkovian]

No bump, as no code changes were made.

[itkovian]

I have no idea why this is suddenly failing

FAIL: test_timeout (test.run.TestRun)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/var/lib/jenkins/jobs/hpcugent_github.com/jobs/vsc-base/branches/PR-360/workspace/test/run.py", line 286, in test_timeout
    do_test(False)
  File "/var/lib/jenkins/jobs/hpcugent_github.com/jobs/vsc-base/branches/PR-360/workspace/test/run.py", line 264, in do_test
    self.assertFalse(check_pid(pids[depth]), f"main depth={depth} pid (pids {pids}) is killed by timeout")
AssertionError: True is not false : main depth=2 pid (pids [1137337, 1137335, 1137332]) is killed by timeout

[wdpypere]

@itkovian it happens when the build host is a bit overloaded, which it was this morning. I'll retrigger the tests.