Fix Spark Streaming gracefully shutdown on Hadopp 2.8.x

Gracefully shutdown is not properly working on Hadoop 2.8.x. Hadoop introduces 10 seconds timeout by default. This is hardcoded and not something that we can configure with Hadoop settings.

https://github.com/apache/hadoop/blob/branch-2.8.5/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/util/ShutdownHookManager.java#L51

However, if we use 

public void addShutdownHook(Runnable shutdownHook, int priority, long timeout, TimeUnit unit)

in https://github.com/apache/spark/blob/master/core/src/main/scala/org/apache/spark/util/ShutdownHookManager.scala#L180

problem might be solved.