Those are all consumed by our parser, so they all support comments.
I was considering whether they should have a license header at all,
but in the end I decided to add it because those files are often created
by copying parts of real unit files. And if the real ones have a license,
then those might as well. It's easier to add it than to make an exception.
test-loop-block needs to run in qemu, so we are currently not
testing it in the CI. Run it by itself in a separate job from
TEST-02-UNITTESTS to avoid slowing that suite down.
Fixes https://github.com/systemd/systemd/issues/19966
Disable it in the bionic-* CI for now, as it's affected by
the same uevent ordering issue as TEST-50-DISSECT which makes
it flaky.