Add Neutron flake8/pep8 setting

* This also fixes the warnings generated by "tox -e pep8"

Change-Id: I15e7ff1e6aa20f5a228db853e8b39ecd9da84436
Signed-off-by: Joe Mills <joe@midokura.com>
Merge "Add Neutron flake8/pep8 setting"