restore nested login in gdm

[David]

Hi, I am a long time user of gdm nested logins. However, they do not exist in gdm3 :( . Before I created new logins via the command "gdmflexiserver -n" which would bring up another gdm login window inside a Xephyr container. This functionality is rather useful, partly because there isn't an apparmor XACE implementation at the present time and party because it is (in general) a useful thing :p

There is a bug filed in the upstream at https://bugzilla.gnome.org/show_bug.cgi?id=624370 with a patch to restore the functionality it would be awesome if this was applied in ubuntu!