Comment # 3 on bug 1129476 from Bruno Pesavento

Trying to debug this problem, I saw that the problem doesn't show up if booting
with the following sequence.
> boot to multi-user.target (just adding '3' to the boot command line)
> login as root and issue 'systemctl isolate graphical.target' on VT1
> login as normal desktop user via GDM (desktop shows on VT2)
> logout as 'root' from VT1
> work on the desktop (VT2) as usual, reboot or shutdown from desktop when finished.
To me that looks like something goes wrong in the 'default' boot sequence,
maybe the graphical target is started too soon on this HW (fast SSD  and i7
4700HQ here) and starting it manually a few seconds later sorts things out?
Tried that 5 times with no problem; tried again the 'default' boot directly to
graphical desktop and the nasty 1m30s delay at shutdown was still there...
Hope this helps somebody make sense of this annoying situation.