Merge pull request #461 from pwendell/master

Use renamed shuffle spill config in CoGroupedRDD.scala

This one got missed when it was renamed.

core/src/main/scala/org/apache/spark/rdd/CoGroupedRDD.scala

@@ -106,7 +106,7 @@ class CoGroupedRDD[K](@transient var rdds: Seq[RDD[_ <: Product2[K, _]]], part:
 
   override def compute(s: Partition, context: TaskContext): Iterator[(K, CoGroupCombiner)] = {
     val sparkConf = SparkEnv.get.conf
-    val externalSorting = sparkConf.getBoolean("spark.shuffle.externalSorting", true)
+    val externalSorting = sparkConf.getBoolean("spark.shuffle.spill", true)
     val split = s.asInstanceOf[CoGroupPartition]
     val numRdds = split.deps.size