nixos: fix linux containers (systemd-nspawn, lxc, lxc-libvirt)

- Make dhcp work, use dhcpcd without udev in container
- Make login shell work, patch getty to not wait for /dev/tty0
- Make ssh work, sshd/pam do not start session

pkgs/os-specific/linux/systemd/default.nix

@@ -22,6 +22,7 @@ stdenv.mkDerivation rec {
     [ # These are all changes between upstream and
       # https://github.com/edolstra/systemd/tree/nixos-v203.
       ./fixes.patch
+      ./fix_console_in_containers.patch
     ]
     ++ stdenv.lib.optional stdenv.isArm ./libc-bug-accept4-arm.patch;
 

pkgs/os-specific/linux/systemd/fix_console_in_containers.patch

@@ -0,0 +1,14 @@
+diff -ruN systemd-203/units/getty@.service.m4 systemd-203-patched/units/getty@.service.m4
+--- systemd-203/units/getty@.service.m4	2013-01-07 22:50:49.083315575 +0100
++++ systemd-203-patched/units/getty@.service.m4	2014-03-18 09:54:40.002476232 +0100
+@@ -23,7 +23,9 @@
+ # On systems without virtual consoles, don't start any getty. (Note
+ # that serial gettys are covered by serial-getty@.service, not this
+ # unit
+-ConditionPathExists=/dev/tty0
++ConditionPathExists=|/dev/tty0
++ConditionVirtualization=|lxc
++ConditionVirtualization=|lxc-libvirt
+ 
+ [Service]
+ # the VT is cleared by TTYVTDisallocate