When weasel told me about this, he did say it was optional. And in
practice, nevii is fast enough: it runs `ud-replicate` every 5 minutes
(like everyone else) and so syncs DNS changes with the LDAP server
fast enough so that we don't need ot bother with this.

This makes it easier to edit the copy-paste.

The grml-debootstrap install process properly sets up sources.list
with security upgrades, and we should expect the same of any install
process.

That's a pre-requisite of the new-machine setup, which we failed to
fulfill.

Instead we'll copy authorized keys in a hook ourselves.

This is so we have one less thing to do by hand in the installer.

We need to copy this into the password manager so it *needs* to be
obvious here.

Normally, the --defaultinterfaces command *should* setup a proper file
for us, including automatic config for eth0. Let's see if it works
next time.

tsa-misc is not exactly a pre-requisite: none of the installers
currently deploy it, and it might eventually go away if we go the
"remote bootstrap" way.