Just fixing comment that shows usage

Author: anant asthana <anant.asty@gmail.com>

Closes #2948 from anantasty/patch-1 and squashes the following commits:

d8fea0b [anant asthana] Just fixing comment that shows usage

examples/src/main/python/streaming/hdfs_wordcount.py

@@ -21,7 +21,7 @@
    <directory> is the directory that Spark Streaming will use to find and read new text files.
 
  To run this on your local machine on directory `localdir`, run this example
-    $ bin/spark-submit examples/src/main/python/streaming/network_wordcount.py localdir
+    $ bin/spark-submit examples/src/main/python/streaming/hdfs_wordcount.py localdir
 
  Then create a text file in `localdir` and the words in the file will get counted.
 """