This is broken because it requires restarting applications to see new
NSS modules. The proper way to handle NSS modules is through nscd.
See commit 554ae9908b4abd45c9769da023470ae2c12ebdfd.
empty now), do more of bashrc.sh declaratively, and moved nsswitch
generation to modules/config/nsswitch.nix.
svn path=/nixos/branches/modular-nixos/; revision=15754