#382 Arrow key not working in dropdown

Testcase to check arrow key in dropdowns

1. Open Order window

2. Add a bpartner then press tab to get to Price System field

3. use the up and down arrows to select any price system
   • => both arrows work
4. press enter to select the price system
   • => price system is selected
5. press tab to get to other fields
   • => next field is selected, price system is saved

6. check other window, e.g. Product

7. use tab to navigate through fields

8. find a dropdown with lots of entries (e.g. statistics group)
   • => notice that there is a scrollbar
9. use up and down arrow to select one
   • => both arrows work
   • => the scrollbar also moves down with the arrow