[SPARK-4253]Ignore spark.driver.host in yarn-cluster and standalone-cluster mode

And I see description in configuration document is "This is used for communicating with the executors and the standalone Master.",  should we modify it together?
Substring search seems like a dangerous / brittle way to detect whether we're running in a cluster deployment mode, since it's plausible that a user might have a master hostname which also contains cluster, e.g. "spark://testcluster".