This test runs fine locally (both on Qemu and nspawn) but sporadically fails on
autopkgtest for some reason.
Disable it while the issue is investigated to reduce noise.
The time-based cache allows starting a new unit without an expensive
daemon-reload, unless there was already a reference to it because of
a dependency or ordering from another unit.
If the cache is out of date, check again if we can load the
fragment.