This used to work only when specified via the command line
or if systemd was not being used. However, the exisistence of
20_force_driver.conf also requires dracut-pre-udev.service
to be run.
Reference: bsc#986216
Basic systemd functionality is in 00systemd now.
Switching root and the initrd.target is in 00systemd-initrd.
Dracut additions to the systemd initrd are in 98dracut-systemd.