Boost correct layer for Recents Go transition

For transition from app to fallback recents, the apps were on the same
Z-layer causing both to show up in the animation. We should instead
boost the closing app so that it's visually on top as it shrinks down.

Bug: 114136250
Test: Press overview in app to go to recents, behaves as expected
Change-Id: Iaca1e4fc1486721468a5bfffb1d139259d48739f