Initialize dispatcher logging configuration

def init_dispatcher_logger():
    """ Initialize dispatcher logging configuration"""
    logger_file_path = 'dispatcher.log'
    if dispatcher_env_vars.NNI_LOG_DIRECTORY is not None:
        logger_file_path = os.path.join(dispatcher_env_vars.NNI_LOG_DIRECTORY, logger_file_path)
    init_logger(logger_file_path, dispatcher_env_vars.NNI_LOG_LEVEL)