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.
Currently we are making MBR disk images for qcow2 and partitioned disk,
so the UEFI packages aren't required at this point.
Move the clearpart command into compose.py so that in the futute it can
use clearpart --disklabel to create a GPT image, and add the required
packages to the package set.
