add and pass all the unit tests of scheduler
add and pass all the unit tests of scheduler

apache/incubator-singa,nudles/incubator-singa,apache/incubator-singa,apache/incubator-singa,nudles/incubator-singa,apache/incubator-singa,nudles/incubator-singa,apache/incubator-singa,nudles/incubator-singa,nudles/incubator-singa