Putting any configuration into /etc/net/ifaces/lo/resolv.conf
makes etcnet *overwrite* /etc/resolv.conf, while putting that
into /etc/resolv.conf itself makes e.g. vzctl --nameserver
*append* to what's been specified.
Reported-by: Gleb Fotengauer-Malinovskiy <glebfm@altlinux.org>

Refer to net-dns feature where appropriate
(it actually started out as an extension of
net feature but the reasons to separate it
quickly became apparent to me).

Using just a single one of those tends to end up problematic
at times but any two use to suffice.

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.