Do not call drawableChanged pre Q

Some apps rely on not updating the window format when changing the
background of the DecorView. To keep the compatibilty with these app we
add only call DecoreView.drawableChanged() when the window background is
changed on app targetting Q and above.

Test: Manually test by lunching Instagram TV and pressing return twice.
The window should aninate with no flickering.
Bug: 136987724

Change-Id: I3593d30dc6f10519008151974e475f0dad86fc64