Fix Shade background flicker at the beginning of transition

This change fixes the flicker when transitioning from SingleShade to QS
Scene by disabling the broken touch indication on the
NotificationScrollingStack (only when onEmptySpaceClick is not null).

The removal of the touch indication also has a performance improvement,
and is as intended.

Fix: 440593535
Test: manual, drag on single shade to transit to QS scene, should not have flicker
Flag: com.android.systemui.scene_container
Change-Id: I6c19b15022655036ad7e3ca6950e6be632c21066