Since these images can be used to create multiple machines, they should
not have a unique machine-id attached to them. Replace /etc/machine-id
with an empty file so that it will be regenerated at boot time.
This differs from lmc's --make-ami in that creates a full disk image instead of
an fsimage. Create a raw disk image with a / and /boot partitions, and enable
sshd, chronyd, and cockpit by default.
(cherry picked from commit 18188bf6cf)
