Fix lockscreen flash when closing activities

When closing activities over the lockscreen, transition directly to the
hub by snapping in the hub. This prevents flashing the lockscreen.

Fixes: 340954631
Test: see videos on bug, verified with timers and media activities
Flag: com.android.systemui.communal_hub
Change-Id: Id06341bf88ead966eba6d3e0a26d8e4f0e692864