BREAKING CHANGE: bblayers.conf / bblayers.conf.sample of project
using CoreOS should be adapted to use external-layers instead
of layers for each moved layers
We are now using efibootguard to provide a A/B boot path for
the kernel and the rootfs.
This commit remove some change for systemd/systemd-boot that are
not needed anymore and rework how we set the command line, as we
will need to have the command line argument of the kernel both
inside do_image_wic and in a future do_image_swu
Samuel Dolt
Patrick Vogelaar