Comment # 60 on bug 1055641 from Franck Bui

(In reply to Olli Tuominen from comment #59)
> (In reply to Franck Bui from comment #57)
> > Please at the *shutdown* stage, issue the following command:
> > 
> >  - cat /proc/mounts
> 
> missing the /oldroot
> 
> >  - dmsetup info -v system-root
> 
> Device does not exist

I'm puzzled...

According to your comment #32, "dmsetup remove" is supposed to the failing
command. And this command is executed by
lib/dracut/hooks/shutdown/25-dm-shutdown.sh.

In its turn this script is supposed to be called between "pre-shutdown" and
"shutdown"  by /shutdown.

Can you comment the changes in /usr/lib/dracut/modules.d/99shutdown/shutdown.sh
requested in comment #51, recreate the initrd and retry ?