Comment 6 for bug 1673215

Confirmed.

The problem is unity8 crashes/exits for the second user, right after:

[2017-03-16:09:39:09.588] QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-testuser'
[2017-03-16:09:39:09.588] qtmir.screens: ScreensModel::ScreensModel
[2017-03-16:09:39:09.589] QSocketNotifier: Can only be used with threads started with QThread
[2017-03-16 09:39:09.592597] mirplatform: Found graphics driver: mir:mesa-kms (version 0.26.1)
[2017-03-16 09:39:09.592630] mirplatform: Found graphics driver: mir:mesa-x11 (version 0.26.1)
[2017-03-16 09:39:09.592766] mirplatform: Found graphics driver: mir:stub-graphics (version 0.26.1)
[2017-03-16 09:39:09.592775] mirplatform: Found graphics driver: throw-on-creation (version 0.26.1)
[2017-03-16 09:39:09.593183] mirserver: Starting
[2017-03-16 09:39:09.607913] mirserver: Using nested cursor
[2017-03-16:09:39:09.608] qtmir.mir: PromptSessionListener::PromptSessionListener - this= PromptSessionListener(0x7fe14c16bc50)
[2017-03-16:09:39:09.608] qtmir.mir: PromptSessionListener::~PromptSessionListener - this= PromptSessionListener(0x7fe14c16bc50)
[2017-03-16:09:39:09.610] bind: Permission denied

Also confirmed the high CPU usage that follows. That's unity8-dash for the second user continuously restarting (because there is no server for it to connect to) -> bug 1578469