apache/spark — pull request #3806 by XuTingjun (2014-12-26 02:34:43+00:00)
Title: specify AM core in yarn-client and yarn-cluster mode

I add some configurations below.
spark.yarn.am.cores/SPARK_MASTER_CORES/SPARK_DRIVER_CORES for yarn-client mode;
spark.driver.cores for yarn-cluster mode.