Fix TaskView over lockscreen

When launching the TaskView with embedded activity over lockscreen,
the ControlsActivity is being issued onPause()/onResume()
calls. Previously, these would trigger show and hide animations to
run, which means it would also immediately hide the TaskView. Move
these to onStart()/onStop()

Fixes: 226117798
Test: ControlsMockApp with test activities
Change-Id: If888859ed733a4b683d164d96d0893ddb1e8a106