Ignore calls to Control::setRedraw(false) if the control contains any
embedded application as a child.

This change does not completely get rid of the flickering but it reduces
it drastically.

Contributes to
https://github.com/eclipse-platform/eclipse.platform.swt/issues/1122

Co-authored-by: Federico Jeanne <Federico.Jeanne@vector.com>
Co-authored-by: Heiko Klare <Heiko.Klare@vector.com>