Cleanup swipe detector in case of double cancel

We manually dispatch cancel when returning to the previous state in
onDragEnd(), but could end in a bad state if getting a second,
external cancel (e.g. by pressing home). Thus, we restore the
onCancelListener after manually dispatching cancel.

Bug: 79258868
Change-Id: Idc4c33cede1d8af1829a4a744b9348d379bcf8f7