Cleanup mAnimatingExit flag before maybeUpdateTransitToWallpaper()

Cleanup mAnimatingExit flag before maybeUpdateTransitToWallpaper()

If we get onStopped before next resume, but previous exit animation
doesn't finish by the time the entering animation is started,
notifyAppResumed() won't do a surface cleanup (since it's already
stopped). Then maybeUpdateTransitToWallpaper() will think the wallpaper
target (launcher) is invisible because of the mAnimatingExit==true,
thus fails to pick WALLPAPER_OPEN animation.

We need to clear mAnimatingExit and relevant flags before
maybeUpdateTransitToWallpaper(). Currently we do it in handleOpeningApps
but that's too late.

bug: 30255354
Change-Id: Idb049c54978824709a190c413d82d42f40226aa7