The feature is also useful for pure wayland.

For rootfs a similar script is launched when building image.

This reverts commit 81231ae5:
task #122722 contains a few display managers updated for
systemd-214.

systemd-214 has broke things badly enough so that
graphical boot target is not effective anymore;
enabling prefdm explicitly helps though.

It has value of its own and can be used standalone;
autologin does require autostart though.

Adjust x11 feature targets accordingly.