Fix neutron-tempest-plugin tox pep8 setup

The plugin pep8 setup was failing due to trying to use upper-constraints
with the pip install -e ., with a version constraint error. Grab
the setup commands from the neutron tox.ini to fix this.

Change-Id: Ic7b6e80213aafac6df7b0a8b044fe45f60870483
1 file changed