* Do not create a dummy shell for parent. This caused the
  implementation of getPrimaryClientArea() to never fall
  back to the primary monitor.

* Fine-tune position of the popup by taking the usable client area
  of the parent shell into account.

Change-Id: I877ed5357ef2e1cd97eccb6f3454bd60cba18c87
Signed-off-by: Sebastian Ratz <sebastian.ratz@sap.com>