Systemd v243 is complaining about the wrong substitution there. That is
sort of harmless, because systemd-udevd in that version doesn't need the
rule anyway. But still fix it, to avoid a warning.
Also, newer udevd's $PATH doesn't include sbin. That is also okay,
because we don't need the rule to actually work there. But fix it
anyway.
https://bugzilla.redhat.com/show_bug.cgi?id=1740655
(cherry picked from commit 27d380b70e)
Those are not required with systemd-udevd v210 or newer. This way
distros which have a new enough version of udev can skip installing
84-nm-drivers.rules. While at it, don't use absolute paths for sed and
ethtool.