title: Celery autodiscover_tasks not working for all Django 1.7 apps
body: <p>I have a Django 1.7 project with Celery 3.1. All the apps in my Django project work with the new AppConfig. The problem is that not all the tasks are found with <code>autodiscover_tasks</code>:</p>
  
  <pre><code>app.autodiscover_tasks(settings.INSTALLED_APPS)
  </code></pre>
  
  <p>If i use autodiscover_tasks like this it wil work:</p>
  
  <pre><code>app.autodiscover_tasks(settings.INSTALLED_APPS + ('apps.core','apps.sales'))
  </code></pre>
  
  <p>The tasks defined in websites are found but the tasks in core and sales are not. All have the same layout with <code>apps.py</code> and <code>tasks.py</code>.</p>
  
  <p>The project folder structure is:</p>
  
  <pre><code>apps
    core
    apps.py
    tasks.py
  dashboard
    apps.py
  sales
    apps.py
    tasks.py
  websites
    apps.py
    tasks.py
  </code></pre>
  
  <p>The class definitions are as follows:</p>
  
  <pre><code>class WebsitesConfig(AppConfig):
      name = 'apps.websites'
      verbose_name = 'Websites'
  
  class SalesConfig(AppConfig):
      name = 'apps.sales'
      verbose_name = 'Sales'
  </code></pre>