Two bugs are addressed.
1) The sysprep element was broken in that it only truncates
/etc/machine-id, but not /var/lib/dbus/machine-id. systemd will
not generate a new machine-id if /var/lib/dbus/machine-id is
present[1], it will simply copy it to /etc/machine-id.
We observed machine-ids being packaged in /var/lib/dbus/machine-id
on several distros: Ubuntu Bionic, Fedora 29, Debian Stretch.
CentOS 7 and Ubuntu Xenial do not contain packaged machine-id as
far as I can tell.
All test builds were performed using -minimal elements.
2) A second bug existed where debian-minimal did not run the sysprep
element at all, so a stretch image I tested contained a populated
/etc/machine-id AND a populated /var/lib/dbus/machine-id.
[1] https://www.freedesktop.org/software/systemd/man/machine-id.html#Initialization
Change-Id: Ibb28b6e90d966a845de38a2cd5a1e8babd2604bc
c7e907794c