Add back recents staggering entrance animation

Since there was a change in ValueAnimator that did not allow setting
initial play time per interpolator grouped in an AnimatorSet, set the
initial play time for each animation to allow the same effect.

Change-Id: I05445bde6e185a99250d7d193bd0e74d5ce98fa0
Fixes: 36175824
Test: manual - launch recents