Decode default argv into Unicode on Python 2 (Python 3 does this
under the covers).
Backport of OSC change https://review.openstack.org/#/c/343035/
Co-Authored-By: John Dennis <jdennis@redhat.com>
Related-Bug: 1603494
Change-Id: I192f17962bb5e21c20c3743b8f3e88c2450432c7