Default pep8/fast8 to run under python 3
Default pep8/fast8 to run under python 3

There are slight differences with pep8 when run under python 3.
It is a little more strict on certain things, plus we want to
get to just supporting python 3 eventually, so this switches
over the pep8 and fast8 targets to use python 3.

Change-Id: I3212bfb2dd173e79dae6d548827a803f68923da9

phenoxim/cinder,mahak/cinder,openstack/cinder,mahak/cinder,phenoxim/cinder,openstack/cinder