bugfix: play/pause state not right

tower: https://tower.im/projects/d4e0ff64158645f28d99a9ca72d0c27b/todos/41402b66496145a391998be5b4bb8351/

remove the unreliable binding thing, change the propery value on
the changed signal fired

Change-Id: Ib77117b796d3072052fe97b58e3e1ec8097ccc99