Fix the test, we should be looking at the second element instead

mllib/src/test/scala/org/apache/spark/mllib/util/MLUtilsSuite.scala

@@ -139,7 +139,7 @@ class MLUtilsSuite extends FunSuite with LocalSparkContext {
             "Each training+validation set combined should contain all of the data.")
         }
         // K fold cross validation should only have each element in the validation set exactly once
-        assert(foldedRdds.map(_._1).reduce((x,y) => x.union(y)).collect().sorted ===
+        assert(foldedRdds.map(_._2).reduce((x,y) => x.union(y)).collect().sorted ===
           data.collect().sorted)
       }
     }