fix init args for boto single file writer
fix init args for boto single file writer

pearsonlab/thunder,mikarubi/thunder,oliverhuangchao/thunder,jwittenbach/thunder,kcompher/thunder,j-friedrich/thunder,kunallillaney/thunder,zhwa/thunder,poolio/thunder,mikarubi/thunder,broxtronix/thunder,thunder-project/thunder,poolio/thunder,pearsonlab/thunder,zhwa/thunder,kunallillaney/thunder,kcompher/thunder,j-friedrich/thunder,broxtronix/thunder,oliverhuangchao/thunder