Bug#1019035: systemd-cron: prerm fails in unbooted systems

[Alexandre Detiste]

> Thank you in advance for your consideration. I hope you will agree this
> is a bug and apply the (trivial) patch, not send me away with an
> admonishment that this is user error. :)

I actually do the same kind of "not booted filesystem manipulation in
an chrooted overlayfs"
for the Debian-derived distro I'm building at work.
It's horrible, but it has to work.

Thanks for comparing with what the debhelper snippet is doing,
I should have done this aniway.

Thanks