[SPARK-5234][ml]examples for ml don't have sparkContext.stop

JIRA issue: https://issues.apache.org/jira/browse/SPARK-5234

simply add the call.

Author: Yuhao Yang <yuhao@yuhaodevbox.sh.intel.com>

Closes #4044 from hhbyyh/addscStop and squashes the following commits:

c1f75ac [Yuhao Yang] add SparkContext.stop to 3 ml examples

examples/src/main/scala/org/apache/spark/examples/ml/CrossValidatorExample.scala

@@ -106,5 +106,7 @@ object CrossValidatorExample {
       .foreach { case Row(id: Long, text: String, score: Double, prediction: Double) =>
       println("(" + id + ", " + text + ") --> score=" + score + ", prediction=" + prediction)
     }
+
+    sc.stop()
   }
 }

examples/src/main/scala/org/apache/spark/examples/ml/SimpleParamsExample.scala

@@ -97,5 +97,7 @@ object SimpleParamsExample {
       .foreach { case Row(features: Vector, label: Double, prob: Double, prediction: Double) =>
         println("(" + features + ", " + label + ") -> prob=" + prob + ", prediction=" + prediction)
       }
+
+    sc.stop()
   }
 }

examples/src/main/scala/org/apache/spark/examples/ml/SimpleTextClassificationPipeline.scala

@@ -85,5 +85,7 @@ object SimpleTextClassificationPipeline {
       .foreach { case Row(id: Long, text: String, score: Double, prediction: Double) =>
         println("(" + id + ", " + text + ") --> score=" + score + ", prediction=" + prediction)
       }
+
+    sc.stop()
   }
 }