title: Get current celery task id anywhere in the thread
body: <p>I'd like to get the task id inside a running task,
  without knowing which task I'm in.
  (That's why I can't use <a href="https://stackoverflow.com/a/8096086/245024">https://stackoverflow.com/a/8096086/245024</a>)</p>
  
  <p>I'd like it to be something like this:</p>
  
  <pre><code>@task
  def my_task():
      foo()
  
  def foo():
      logger.log(current_task_id)
  </code></pre>
  
  <p>This pattern returns in many different tasks, and I don't want to carry the task context to every inner method call.</p>
  
  <p>One option could be to use the thread local storage, but then I will need to initialize it before the task starts, and clean it after it finished.</p>
  
  <p>Is there something simpler?</p>