Major Description
With batched write ahead log on by default in driver (SPARK-11731), if there is no receiver based InputDStream, the "BatchedWriteAheadLog Writer" thread created by BatchedWriteAheadLog never get shutdown.
The root cause is due to https://github.com/apache/spark/blob/master/streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceiverTracker.scala#L168
that it never call ReceivedBlockTracker.stop() (which in turn call BatchedWriteAheadLog.close()) if there is no receiver based input.
