overlay/live-generator : systemd-udev-settle is deprecated

[jbtrystram]

I saw this today while playing with a raspberry pi.

fedora-coreos-config/overlay.d/05core/usr/lib/dracut/modules.d/35coreos-live/live-generator

Line 95 in 848c6f5

Wants=systemd-udev-settle.service

the man page discourage to use this service. I had the issue where having a couple of usb peripherals plugged to the Pi made the initramfs enter the emergency shell because udev-settle timed out

[jlebon]

Ideally, we'd drop it, but we'd need to make sure that we're not re-introducing the race it was intending to hack around (#437). I don't think that was ever fully debugged.