Add autopep8 to tox.ini

autopep8 is an automated code formatting tool for python,
it does not know everything, also not super fast,
but it is faster than I can manually reformat the code.

tools/format.sh will call the formatting,
the tox will check did you called it.

Also adding a tox -eautopep8 way to use it.

autopep8 formats the lines in one way,
where tempest used a another way it was changed.

Change-Id: I6d51b14a5a5b87761071d0927fca23ba1651aa41
diff --git a/tempest/scenario/manager.py b/tempest/scenario/manager.py
index dbb9acc..5f4fb29 100644
--- a/tempest/scenario/manager.py
+++ b/tempest/scenario/manager.py
@@ -166,7 +166,7 @@
                         clients.security_groups_client.list_security_groups(
                         ).get('security_groups')
                     sec_dict = dict([(s['name'], s['id'])
-                                    for s in security_groups])
+                                     for s in security_groups])
 
                     sec_groups_names = [s['name'] for s in kwargs.pop(
                         'security_groups')]