50-setup-network was a hasty hack (surprise!) that used to do
what net and net-eth features have been created to do since;
just drop the duplicated crufty code.

Unconditional resolver setup isn't done now: those with static
setup are better off doing it explicitly, and those with DHCP
should be fine already.

NB: /etc/hosts *is* fine within setup package *but* hasher will
    overwrite it with a copy of host's one; let's reset contents
    to initial at least until hasher gets fixed and the fix is
    rather deployed in the wild.