failed logins result in zombie lightdm processes

[Matt Fischer]

versions:
Ubuntu 12.04, just updated
lightdm 1.2.1-0ubuntu1 Display Manager

Failed logins result in zombie lightdm processes. The example below shows the result of 6x failed login attempts. A successful login does not clear the zombies.

root 1703 0.0 0.0 0 0 ? Z 12:02 0:00 [lightdm] <defunct>
root 1707 0.0 0.0 0 0 ? Z 12:02 0:00 [lightdm] <defunct>
root 2670 0.0 0.0 0 0 ? Z 14:35 0:00 [lightdm] <defunct>
root 2674 0.0 0.0 0 0 ? Z 14:35 0:00 [lightdm] <defunct>
root 2717 0.0 0.0 0 0 ? Z 14:35 0:00 [lightdm] <defunct>
root 2930 0.0 0.0 0 0 ? Z 14:37 0:00 [lightdm] <defunct>

This is probably related to:

#990661 many lightdm zombie process created while press many Escape button on Login screen
#993573 LightDM leaves zombie processess when switching users

But I wanted to file anyway since my repro steps are different.