I was able to reproduce this bug (Ubuntu 16.04.1 + xfce). I used a test program rather than MediaTomb. When I tried to shutdown, I was presented an authentication popup as above and when I Esc'd out of it, I was logged out and the inhibited process was killed. The system did not shutdown.
Subscribing Xubuntu-developers, please have a look. -- You received this bug notification because you are a member of Xubuntu Developers, which is subscribed to the bug report. https://bugs.launchpad.net/bugs/1615612 Title: systemd-inhibit authentication ignored by suspend request To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xfce4-power-manager/+bug/1615612/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~xubuntu-dev Post to : [email protected] Unsubscribe : https://launchpad.net/~xubuntu-dev More help : https://help.launchpad.net/ListHelp

