LDM2 prompts three times for password before asking for username

This is arguably a bug or a feature.

Some users have complained about LDM2 prompting up to 3 times for a password before re-asking for the username. Evidently this is a problem particularly with young children who will frequently get type the username wrong and then can't see the fact that it was typed wrong. If prompting for the password 3 times is desirable, it should probably be optional.

https://lists.ubuntu.com/archives/edubuntu-users/2007-November/thread.html#2636

Suggested solutions:

1. Keep current behaviour, but when prompting for the password, display the username somewhere.

2. Modify to only prompt once for the password by either of:
    a. Append "NumberOfPasswordPrompts 1" to the end of ltsp_chroot:/etc/ssh/ssh_config or create ltsp_chroot:/etc/ltsp/ssh_config and patch ldm to pass "-F /etc/ltsp/ssh_config" to ssh.
    b. Patch LDM2 to pass the "-o NumberOfPasswordPrompts=N" direct to ssh (as in the thread).

In a sense it might be good to have [1] and one of [2a] and [2b].