Drop the interface renaming disabling hack

Drop the interface renaming disabling hack

- it won't work with current systemd, as the udev rules file name
  changed. The /dev/null symlink does nothing now.
- the interface won't be renamed when systemd-network is not installed
- PLD really should not force its ways for historical reasons. eth*
  unpredictability is a real problem on systems with more than one
  interface.

Predictable interface names will be used when systemd-networkd is
installed, unless its configuration states otherwise.

Without systemd-networkd installed eth* hell stays.