ActiveQt server windows are always created top level

Steps to repro:

1) Build qtactiveqt\examples\activeqt\simple
2) Build qtactiveqt\tools\testcon
3) Run testcon
4) Insert control "QSimpleAX Class"
--> The control is displayed on separate toplevel window instead of contained in the MDI subwindow.

Opening native controls such as "Windows Media Player" work as expected.