dracut: remove junk from zz-default.network
dracut: remove junk from zz-default.network

This snuck in from experimentation and should never have been merged.
It's being ignored by systemd-networkd, since .network files not
actually systemd units.

coreos/bootengine,yuwata/bootengine,andrejro/coreos--bootengine,coreos/ignition,coreos/ignition,coreos/ignition