Start some worker class.

    :param str which_worker: name of the worker
    :param dict config: ``rejester`` config block

def start_worker(which_worker, config={}):
    '''Start some worker class.

    :param str which_worker: name of the worker
    :param dict config: ``rejester`` config block

    '''
    if which_worker == 'multi_worker':
        cls = MultiWorker
    elif which_worker == 'fork_worker':
        cls = ForkWorker
    else:
        # Don't complain too hard, just fall back
        cls = ForkWorker
    return run_worker(cls, config)