Made spark_ec2.py PEP8 compliant.

The change set is actually pretty small -- mostly whitespace changes. Admittedly this is a scary change due to the lack of tests to cover the ec2 scripts, and also because indentation actually impacts control flow in Python ...

Look at changes without whitespace diff here: https://github.com/apache/spark/pull/891/files?w=1

Author: Reynold Xin <rxin@apache.org>

Closes #891 from rxin/spark-ec2-pep8 and squashes the following commits:

ac1bf11 [Reynold Xin] Made spark_ec2.py PEP8 compliant.