ove QEMU (and other NixOS instances that use a remote filesystem like
NFS):
* Don't take down the network interfaces during shutdown.
* Don't try to unmount the Nix store. Usually, this doesn't work
because it's still in use, but on remote filesystems like CIFS the
`-f' umount flag actually works.
svn path=/nixos/branches/modular-nixos/; revision=16036