Disable PaintRedirector when non-composited

Without Compositing we do not really need the PaintRedirector,
it only adds overhead. This reverts the behavior to how it was before
the PaintRedirector was introduced by just not redirecting the paint
in the event filter when compositing is not active. This should have
the lowest impact on the existing source base.

The change breaks at least oxygen window decoration when compositing
is not active as the decoration is no longer double buffered. But
as written this is exactly the behavior as used before 4.3. Given
the push today there should be enough time for all affected decos
to adjust to the change.

REVIEW: 101413