Don't animate in bouncer contents if initiated from dragging

To avoid animating the input views another time after the
user shows the bouncer by flinging (dragging) up on the lockscreen.
Fixes: 428255740
Test: atest BouncerContentTest
Test: fling up on the lockscreen to show bouncer, observe
bouncer shows on fling/drag once as expected
Flag: com.android.systemui.scene_container

Change-Id: Ib01054bbafa71c88f7ea7363a937fbdbdc20b56d