Get the length of a list in Redis

    CLI Example:

    .. code-block:: bash

        salt '*' redis.llen foo_list

def llen(key, host=None, port=None, db=None, password=None):
    '''
    Get the length of a list in Redis

    CLI Example:

    .. code-block:: bash

        salt '*' redis.llen foo_list
    '''
    server = _connect(host, port, db, password)
    return server.llen(key)