Add FLAG_DELAY_TASKBAR_BG_TAG to restrict when taskbar bg anim gets delayed.

We set it only when user swipes up to unstash.

Fixes: 360778703
Test: swipe up to home, long click on taskbar icon before it settles
Flag: com.android.launcher3.enable_scaling_reveal_home_animation
Change-Id: I24ff466ee6730e3739d85307363567cfa1455cbf