To reproduce the bug (celery/billiard#119):

* You will need MySQL and redis server
* Create a virtualenv and install requirements
* Create the database (default use "testdb" on local MySQL)::

    echo 'CREATE DATABASE testdb' | mysql -u root -ptest
    python manage.py syncdb

* start worker with::

    celery -A simple_project worker -l info --concurrency=1

* start a Django shell and MySQL shell

* Submit a task using Django shell::

    import simple_project.celery
    simple_project.celery.take_time.delay()

* Obviously task get killed in soft timeout.
* Killed that will write result to backend. This open a DB connection
* The DB connection is not closed.
* Using MySQL shell, kill the DB connection (simulate drop connection after long inactivity)
* Submit another task:
    * The task will be ran... and finish ! (timeout won't stop it)
* Now additionnal task won't be run.