Respect flake8/pep8 rules

This change updates code to respect flake8/pep8 rules. It changes:

 * correct KeystoneManager.set_client signature
 * correct code indentation
 * remove useless variables
 * support py3X
   * use netaddr instead of ipaddr (not supported by py34)
   * use dict.values instead of dict.itervalues.
 * correct tests
   * "fake.networks[0]['router:external'] = True" update had side
     effects on other tests, fake managers attributes are now builded
     at instantiation to avoid such trouble.

Change-Id: I56943e198c3dc0e28be5f5b799e62f4a6427292c