Use ACTION_UP instead of ACTION_DOWN in handler

We should only refresh UI on ACTION_DOWN, in this case, if nothing has
handled the touch, CentralSurfaces will close QS.

However, when dragging back gesture in QSCustomizer, this is handled
properly as a back action and QSCustomizer is closed.

Test: manual
Fixes: 183172445
Change-Id: I1d31885638a7cddcb5826723ba7562e43bb5e935