def close_thread_queues
      still_active = false
      @mutex.synchronize do
        @thread_name_to_queue.each_value do |queue|
          if queue.active?
            queue.close
            still_active = true
          end
        end
      end
      return still_active
    end
def close_thread_queues
      still_active = false
      @mutex.synchronize do
        @thread_name_to_queue.each_value do |queue|
          if queue.active?
            queue.close
            still_active = true
          end
        end
      end
      return still_active
    end
Closes all thread queues.

 === Return
 result(Boolean):: true if any queues are still active (and stopping)