[SPARK-10660] Doc describe error in the "Running Spark on YARN" page

In the Configuration section, the **spark.yarn.driver.memoryOverhead** and **spark.yarn.am.memoryOverhead**‘s default value should be "driverMemory * 0.10, with minimum of 384" and "AM memory * 0.10, with minimum of 384" respectively. Because from Spark 1.4.0, the **MEMORY_OVERHEAD_FACTOR** is set to 0.1.0, not 0.07.

Author: yangping.wu <wyphao.2007@163.com>

Closes #8797 from 397090770/SparkOnYarnDocError.