I had the same error on Ubuntu 15.10. I don't believe that it has anything to do with theComputers container.
Instead, it appears to me that the Centrify installer is creating a mangled /etc/lightdm/lightdm.conf file (by not processing the \n escape characters correctly, it seems).
The file that it creates looks like:
\n[SeatDefaults]\ngreeter-show-manual-login=true\n
I changed the file to look like this, and then it booted fine (and Centrify seemed to be operating correctly as well):
[SeatDefaults]
greeter-show-manual-login=true
I would encourage someone at Centrify to take a look at the installation script to see what might be causing this error.