bug#38884: guix system roll-back doesn't roll setuid-programs back

[Jakub Kądziołka]

Steps to reproduce:

1. Add a setuid program to your config:

(setuid-programs (cons*
                   (file-append hello "/bin/hello")
                   %setuid-programs))

2. guix system reconfigure
3. Observe that /run/setuid-programs/hello got created
4. Undo the configuration change
5. guix system reconfigure
6. Observe that /run/setuid-programs/hello no longer exists
7. guix system roll-back

Expected behavior:
/run/setuid-programs/hello appears again

Actual behavior:
/run/setuid-programs/hello still doesn't exist

Similarly, when roll-back is supposed to remove a file, it doesn't.

Previously mentioned in https://debbugs.gnu.org/38800.

Regards,
Jakub Kądziołka