update rafiki to the latest commit
update rafiki to the latest commit

nusdbsystem/incubator-singa,nusdbsystem/incubator-singa,kaiping/incubator-singa,apache/incubator-singa,kaiping/incubator-singa,ijingo/incubator-singa,nudles/incubator-singa,ijingo/incubator-singa,nusdbsystem/incubator-singa,nudles/incubator-singa,ijingo/incubator-singa,apache/incubator-singa,ijingo/incubator-singa,apache/incubator-singa,kaiping/incubator-singa,apache/incubator-singa,nudles/incubator-singa,kaiping/incubator-singa,kaiping/incubator-singa,nusdbsystem/incubator-singa,ijingo/incubator-singa,nusdbsystem/incubator-singa,nudles/incubator-singa,apache/incubator-singa,nudles/incubator-singa