Only reload callback on configuration change.

So it'll get zen changes when the volume dialog is not showing.

Change-Id: I0d4220d0a000d74c6994b07b2d5b8562a6a52585
Fixes: 29355577

packages/SystemUI/src/com/android/systemui/volume/VolumeDialog.java

@@ -977,6 +977,7 @@ public class VolumeDialog implements TunerService.Tunable {
             final int density = newConfig.densityDpi;
             if (density != mDensity) {
                 mDialog.dismiss();
+                mZenFooter.cleanup();
                 initDialog();
             }
             updateWindowWidthH();

packages/SystemUI/src/com/android/systemui/volume/ZenFooter.java

@@ -79,18 +79,11 @@ public class ZenFooter extends LinearLayout {
         mZen = controller.getZen();
         mConfig = controller.getConfig();
         mController = controller;
+        mController.addCallback(mZenCallback);
         update();
     }
 
-    @Override
-    protected void onAttachedToWindow() {
-        super.onAttachedToWindow();
-        mController.addCallback(mZenCallback);
-    }
-
-    @Override
-    protected void onDetachedFromWindow() {
-        super.onDetachedFromWindow();
+    public void cleanup() {
         mController.removeCallback(mZenCallback);
     }