Login screen: Login name change not reflected after doing "ipa user-mod ..."

[R. Becke]

ubuntu-14.04.1-desktop-amd64:

After installing free-ipa client:
sudo apt-get install freeipa-client
...
Version: 3.3.4-0ubuntu3.1
...
sudo ipa-client-install --mkhomedir --no-ntp --enable-dns-updates --principal=admin --password=... --unattended

And updating required files:
sudo vi /usr/share/lightdm/lightdm.conf.d/50-unity-greeter.conf
...
[SeatDefaults]
...
greeter-show-manual-login=true
...

sudo vi /etc/pam.d/common-session
...
session required pam_mkhomedir.so skel=/etc/skel/
...

Whenever later the user-name is changed:
ipa user-mod test--s0-v1 --last="lastNameChanged" --cn="cnNameChanged" --displayname="displayNameChanged"
This has no effect on the login screen.

Even removing all cache files has no effect:
sudo rm /var/lib/sss/db/*
sudo rm /var/lib/sss/mc/*
sudo rm -rf /home/LOGIN
sudo rm -rf /var/lib/lightdm/.cache
sudo rm -rf /var/log/wtmp
sudo rm -rf /var/cache/lightdm
sudo rm -rf /var/lib/AccountsService/users/*
sudo rm -rf /var/lib/lightdm-data/*

On the login screen (lightdm) the login name is not picking up any changes.