[Dropdown] Keyboard selection loses position when an item is chosen

[mairatma]

When the user uses the keyboard to navigate the multiple dropdown items, and hits enter to select one of them, the selection goes back to the first item:

The selection shouldn't change at all in this case. This is probably happening because of the way we've hacked semantic's dropdown to allow for selected items to keep showing up in the dropdown menu, even though semantic hides them automatically. Need to find a way to keep the selection position in this case.