initrd-parse-etc: override argv[0] to avoid dracut issue

initrd-parse-etc: override argv[0] to avoid dracut issue

Quoting https://github.com/systemd/systemd/pull/24054#issuecomment-1210501631:
> this would need a patch in dracut, specifically adding the
> systemd-sysroot-fstab-check to the list of installed stuff:
> https://github.com/dracutdevs/dracut/blob/fe8fa2b0cadbb33e27c8dd8b5851548dcd65835c/modules.d/00systemd/module-setup.sh#L47.
>
> I could do this manually in the CI (and I guess I'd have to do it anyway even
> if the patch lands in upstream, since it won't be available in C8S), but it
> should get there first before merging this PR, otherwise it's going to break
> Rawhide.