Make sure Notification#deleteIntent cannot be used to start

activities from background

Remove whitelisting privilege from deleteIntent before it's
sent in cancelNotificationLocked().

Bug: 130619912
Test: manual (with a custom built app that provides
      PendingIntent.getActivity() to
      Notification.Builder.setDeleteIntent())
Change-Id: I8a85b4c32717f958c4ee2fe040b73bceb96d7feb