use private notification for the heads up

HUN only shows if the device is on and unlocked

Change-Id: Ib3f11bb9267b95c88ddb8bef0b321db79d68841b

packages/SystemUI/src/com/android/systemui/statusbar/policy/HeadsUpNotificationView.java

@@ -73,6 +73,7 @@ public class HeadsUpNotificationView extends FrameLayout implements SwipeHelper.
     public boolean setNotification(NotificationData.Entry headsUp) {
         mHeadsUp = headsUp;
         mHeadsUp.row.setExpanded(false);
+        mHeadsUp.row.setShowingPublic(false);
         if (mContentHolder == null) {
             // too soon!
             return false;