Removing rules files would work fine if a) using dpkg and b) udev had left
its rules files as conffiles under /etc. This sort of situation is why dpkg
does not add back deleted conffiles on upgrade. But since udev's rules files
have moved to /lib/udev, deletion of rules files will no longer persist
Now it seems you'd have to create an empty version of the net generator rule
in /etc/udev to override the one from /lib/udev.