Fix text overlap issue when flinging in ManageApplication

The issue is we have a background handler to find app size and set to
summary asynchronously. When flinging quickly, the view being request to
update by the background handler could be scrolled off screen already.
This change forces onPackageSizeChanged update to only happen when it's
not scrolling.

Change-Id: Ia7ccab776c3c789c8d4c0b55104b48e257b9cebf
Fixes: 76176014
Test: manually fling