Creat a new notification to avoid the mTetheredNotificationBuilder changed

Now the method NotificationBuilder.build() is different with m.
it is not creat new notification. But here it need to creat a
new notification to avoid the mTetheredNotificationBuilder
changed. So we use buildInto to replace build

Change-Id: I274ec833de4ade4a778e1937a09d1e6242d92a7f
Signed-off-by: zhouzhijie <zhouzhijie@xiaomi.com>

services/core/java/com/android/server/connectivity/Tethering.java

@@ -747,7 +747,7 @@ public class Tethering extends BaseNetworkObserver implements IControlsTethering
         mLastNotificationId = icon;
 
         notificationManager.notifyAsUser(null, mLastNotificationId,
-                mTetheredNotificationBuilder.build(), UserHandle.ALL);
+                mTetheredNotificationBuilder.buildInto(new Notification()), UserHandle.ALL);
     }
 
     private void clearTetheredNotification() {