I had the problem with my login display on RHEL 6 being wrong. I could not see any of the additional buttons on screen (ie I couldn’t shut down the VM without logging in).

Fixing this was more of a problem than it should have been. Finally found a bug report to Red Hat:
https://bugzilla.redhat.com/show_bug.cgi?id=586117

Thanks to Daryl Herzmann for his solution/hack:

1. Change gdm’s login shell from /sbin/nologin to /bin/bash
2. Set some password for gdm
3. Log into GDM as user gdm (sick, hehe)
4. Run System Preferences -> Display tool to setup mirroring
5. Log out
6. Set gdm’s login shell back to /sbin/nologin
7. (my addition) lock gdm’s account in shadow by replacing password hash with !!