Hide task bar when folding before the new config renders the correct task bar

Currently on folding, onConfigurationChange doesn't return about 0.5sec after the small screen turns on. The old bar is visible on the new screen before a visual jump from rendering the new bar.

While the ideal solution is to figure out what causes the delay, we can mitigate the visual jump by dimming the old bar when folded listener returns folded

Test: repeatedly fold and unfold, observe that there is no glare task bar change in task bar area after folding
Bug: 291562764
Change-Id: Ic6834d2d3b7df01a8ef841dde601cdb6a3e481b0