Remove on drag listener after drag ended

Remove the on drag listener for the drag layer
in the taskbar after ACTION_DRAG_ENDED is received

This is an additional refactoring discussed
in ag/20490352

Bug: 258850827

Test: manually reproduced the steps in the bug
Change-Id: Ibe207001f41d3ba97a8acaf17d633cbd6682fafd
1 file changed