What Mathias Gug was suggesting may be a better solution however not the current method that Ubuntu employs in its [shutdown] scripts. Considering how hard it is to get the other fixes committed as a solution (which do work, I have tested and so have others), I would assume this would be harder to get committed. Mathias suggested a great possibility but did not attach the actual fix or try it so that doesn't help at all unfortunately.
@Max-Ulrich Farber
What Mathias Gug was suggesting may be a better solution however not the current method that Ubuntu employs in its [shutdown] scripts. Considering how hard it is to get the other fixes committed as a solution (which do work, I have tested and so have others), I would assume this would be harder to get committed. Mathias suggested a great possibility but did not attach the actual fix or try it so that doesn't help at all unfortunately.