wayland: Only send artificial mouse up events for xwayland drags

Seat has to handle two types of drags; ones where clients are updated through data device, and xwayland version where the drag target has mouse events sents as pointer events. A mechanism to treat them differently was introduced, but this former xwayland hack was not included. We also don't need to send frame events when in datadevice mode.

This reset of pointer state breaks electron.