[SPARK-22847] [CORE] Remove redundant code in AppStatusListener while assigning schedulingPool for stage

[Ngone51]

What changes were proposed in this pull request?

In AppStatusListener's onStageSubmitted(event: SparkListenerStageSubmitted) method, there are duplicate code:

// schedulingPool was assigned twice with the same code
stage.schedulingPool = Option(event.properties).flatMap { p =>
      Option(p.getProperty("spark.scheduler.pool"))
    }.getOrElse(SparkUI.DEFAULT_POOL_NAME)
...
...
...
stage.schedulingPool = Option(event.properties).flatMap { p =>
      Option(p.getProperty("spark.scheduler.pool"))
    }.getOrElse(SparkUI.DEFAULT_POOL_NAME)

But, it does not make any sense to do this and there are no comment to explain for this.

How was this patch tested?

N/A

[SparkQA]

Test build #4017 has finished for PR 20033 at commit ace04a5.

• This patch fails PySpark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

[vanzin]

Pyspark failures are unrelated. Merging to master.