This ensures that systemd's creation of `/root` works instead
of falling back to what we have in
`/usr/lib/tmpfiles.d/rpm-ostree-0-integration.conf` for
`d /var/roothome 0700 root root -` which in turn ensures
that both the credential values as well as bootc's injection
of a tmpfiles.d snippet for root SSH key works.
https://github.com/containers/bootc/issues/358
Signed-off-by: Colin Walters <walters@verbum.org>