Force shade collapse instead of scroll on swipes from bottom

Switching to clickable prevents any possibility for motion events to
dispatch to the scrollable view by mistake.

Fixes: 369656661
Test: Ran failing E2E tests, e.g. DragDownNotificationShade
Flag: com.android.systemui.scene_container
Change-Id: Ia8187b7d90c20ee41499829dccd054146ffdcdcb