Added test cases for the CancelableTask and CancelableAsyncResult classes.
Added test cases for the CancelableTask and CancelableAsyncResult classes.

ask/celery,WoLpH/celery,frac/celery,WoLpH/celery,ask/celery,frac/celery,cbrepo/celery,cbrepo/celery,mitsuhiko/celery,mitsuhiko/celery