Merge pull request alteryx#144 from liancheng/runjob-clean

Removed unused return value in SparkContext.runJob

Return type of this `runJob` version is `Unit`:

    def runJob[T, U: ClassManifest](
        rdd: RDD[T],
        func: (TaskContext, Iterator[T]) => U,
        partitions: Seq[Int],
        allowLocal: Boolean,
        resultHandler: (Int, U) => Unit) {
        ...
    }

It's obviously unnecessary to "return" `result`.

core/src/main/scala/org/apache/spark/SparkContext.scala

@@ -796,11 +796,10 @@ class SparkContext(
     val cleanedFunc = clean(func)
     logInfo("Starting job: " + callSite)
     val start = System.nanoTime
-    val result = dagScheduler.runJob(rdd, cleanedFunc, partitions, callSite, allowLocal,
+    dagScheduler.runJob(rdd, cleanedFunc, partitions, callSite, allowLocal,
       resultHandler, localProperties.get)
     logInfo("Job finished: " + callSite + ", took " + (System.nanoTime - start) / 1e9 + " s")
     rdd.doCheckpoint()
-    result
   }
 
   /**