[MINOR] Add python3 compatibility in python examples

## What changes were proposed in this pull request?
Add python3 compatibility in python examples

## How was this patch tested?
manual tests

Author: Zheng RuiFeng <ruifengz@foxmail.com>

Closes #12868 from zhengruifeng/fix_gmm_py.

examples/src/main/python/ml/als_example.py

@@ -17,6 +17,10 @@
 
 from __future__ import print_function
 
+import sys
+if sys.version >= '3':
+    long = int
+
 from pyspark import SparkContext
 from pyspark.sql import SQLContext
 

examples/src/main/python/mllib/gaussian_mixture_model.py

@@ -20,6 +20,10 @@ A Gaussian Mixture Model clustering program using MLlib.
 """
 from __future__ import print_function
 
+import sys
+if sys.version >= '3':
+    long = int
+
 import random
 import argparse
 import numpy as np