Not power off after shutdown in Jessie

[Miroslav Skoric <skoric@eunet.rs>]

After upgrading from Wheezy LTS to Jessie, one of my machines having 512 
MB RAM, does not power off when it reached target shutdown. It seems 
some old issue/bug with systemd or else. In fact, everything closes down 
properly except it does not unmount the following:

/run/user/1000
/run/user/106
/var
/home
/tmp

... and hangs there forever. That did not happen in Wheezy. Any idea?