[SPARK-6720][MLLIB] PySpark MultivariateStatisticalSummary unit test for normL1...

... and normL2.
Add test cases to insufficient unit test for `normL1` and `normL2`.

Ref: https://github.com/apache/spark/pull/5359

Author: lewuathe <lewuathe@me.com>

Closes #5374 from Lewuathe/SPARK-6720 and squashes the following commits:

5541b24 [lewuathe] More accurate tests
dc5718c [lewuathe] [SPARK-6720] PySpark MultivariateStatisticalSummary unit test for normL1 and normL2

python/pyspark/mllib/tests.py

@@ -363,6 +363,13 @@ class StatTests(PySparkTestCase):
         self.assertEqual(10, len(summary.normL1()))
         self.assertEqual(10, len(summary.normL2()))
 
+        data2 = self.sc.parallelize(xrange(10)).map(lambda x: Vectors.dense(x))
+        summary2 = Statistics.colStats(data2)
+        self.assertEqual(array([45.0]), summary2.normL1())
+        import math
+        expectedNormL2 = math.sqrt(sum(map(lambda x: x*x, xrange(10))))
+        self.assertTrue(math.fabs(summary2.normL2()[0] - expectedNormL2) < 1e-14)
+
 
 class VectorUDTTests(PySparkTestCase):