Fixed an issue where media could flicker during bypass

When turning off the phone, media could sometimes
flicker in during bypass, because the qs expansion
would become larger than 0.0f. We now keep the
expansion at 0 during screen off

Bug: 189318793
Test: enable bypass, turn off screen.
Change-Id: Ib2b30fb1c96e4b078978b1958747473aa5fc9cfc