Disable fling on layout update after programmatic shade collapse

Shade collapse triggered by three-button-nav can lead to fling expand
on the next layout change. Theoretically this could affect any shade
collapse that doesn't involve a down action on the shade.

Test: verified behavior with logging
Bug: 285798806
Change-Id: Icc044e67177767a5ef1d745d7dfbcdc81e1054ba

packages/SystemUI/src/com/android/systemui/shade/NotificationPanelViewController.java

@@ -1822,6 +1822,7 @@ public final class NotificationPanelViewController implements ShadeSurface, Dump
 
             // Set after notifyExpandingStarted, as notifyExpandingStarted resets the closing state.
             setClosing(true);
+            mUpdateFlingOnLayout = false;
             if (delayed) {
                 mNextCollapseSpeedUpFactor = speedUpFactor;
                 this.mView.postDelayed(mFlingCollapseRunnable, 120);