title: Celery tasks without result write to result backend
body: <p>I have some tasks which should return result, and some tasks that don't.
  I want to force tasks which shouldn't return result not to write anything in result backend (for example None). How can I achieve that in Celery?</p>
  
  <p>For example it's my tasks:</p>
  
  <pre><code>@app.task
  def taskWithResult():
      # ...code...
      return res
  
  @app.task
  def taskWithNoResult():
      # ...code without return...
  </code></pre>
  
  <hr>
  
  <p>And also I have special queue for some others task which also don't return any result, can I mark that queue as with tasks which mustn't write in result backend?</p>