Comment # 67 on bug 1055641 from Olli Tuominen

So I'm little bit lost. 

In Comment 27/29 we figured out that
/usr/lib/dracut/modules.d/90dm/dm-shutdown.sh
causes the messages, right? As the set -x and sleep reveal that it was the
case.

In pre-shutdown the mount is still there and in shutdown it's not.
And if I manually try unmount /oldroot (in pre-shutdown) it works but not with
the "dmsetup -v --noudevsync remove system-root" (as it's active?).