Comment 6 for bug 1322275

Another workaround, at least for those not requiring the a11y-indicator (accessibility menu for visual impaired): removing the a11y-indicator from the lightdm session, seems to prevent the start of the sound-indicator. Hence the sound-indicator does not block the termination of lightdm session, hence the lightdm session vanishes after login.

The indicators started by lightdm are configured in the corresponding 'lightdm-*-greeter.conf' file (for xubuntu its '/etc/xdg/xdg-xubuntu/lightdm/lightdm-gtk-greeter.conf') in the line 'show-indicators='. Deleting the built-in "~a11y" solved the issue for me.

For a proper solution, one would have to investigate, why the sound-indicator is blocking the clean termination of the lightdm session. Maybe its some sort of reincarnation of https://bugs.launchpad.net/ubuntu/+source/lightdm-gtk-greeter/+bug/1290575.