bind() on Task instance was being called twice

In _task_from_fun(), an instance of Task is created at https://github.com/celery/celery/blob/master/celery/app/base.py#L220
This line calls the metaclass of Task.

The metaclass for Task calls bind() at https://github.com/celery/celery/blob/master/celery/app/task.py#L148

So, it should not be required to call bind() again from _task_from_fun() since we are working with the same instance of Task at both the places.