Fix ntpd

Since the 4.2.8 upgrade, ntpd is broken on NixOS:

  Dec 28 19:06:54 hagbard ntpd[27723]: giving up resolving host 1.nixos.pool.ntp.org: Servname not supported for ai_socktype (-8)

This appears to be because DNS resolution doesn't work in chroots
anymore (due to /etc being missing). So disable chroots for now. It's
probably better to use systemd's containment facilities anyway.