Let Band selection start on ACTION_MOVE instead of ACTION_DOWN.

For some reason, returning true for OnInterceptTouchEvents for
ACTION_DOWN does not:

1. Pass the event to onTouchEvent
2. Intercept the rest of the events afterwards (i.e. MOVE events)

We have to return true on an ACTION_MOVE event in order for the rest of
the events to be passed to onTouchEvents. Not sure why that is, but
b/30146357 is tracking this.

Bug: 31274930
Change-Id: I7380462c8f2dff92da14a93e171a539f66190e31