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
27 files changed