Add new --update-chroot-error-on-change option to
build_puavo_device_image.  If something changed, raise an error.
This is for image build: the previous puppet run should have
fixed all fallout after dist-upgrade, if there is still more to change
the puppet rules are probably broken somehow.
Add a command line option for setting release name, so it does
not have to be asked interactively.  Also, do not ask root password
by default, so that root password can be set if --set-root-password
is used.