Comment 8 for bug 1989078

We haven't considered Focal back then.
But this report [1] made me realize that it is there just as much of a problem.
The solution is simple, proven and should face no unexpected hiccups given what/how it does.
Adding a Focal bug task.

In Focal also [2] has not yet landed, but would be needed (and ok to be applied) just as much.
Some of these might only trigger with when used with newer qemu versions (which lock a few more file types), but that is not something we want to restrict by holding it back.

[1]: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1709818/comments/10
[2]: https://gitlab.com/libvirt/libvirt/-/commit/7aec69b7fb9d0cfe8b7203473764c205b28d2905