RMContainerAllocator#handleJobPriorityChange expects application_priority always

  private void handleJobPriorityChange(AllocateResponse response) {
    Priority priorityFromResponse = Priority.newInstance(response
        .getApplicationPriority().getPriority());

    // Update the job priority to Job directly.
    getJob().setJobPriority(priorityFromResponse);
  }

message AllocateResponseProto {
..
  optional hadoop.common.TokenProto am_rm_token = 12;
  optional PriorityProto application_priority = 13;
  optional CollectorInfoProto collector_info = 14;
..
}