Fix program name in --version output

Neutron currently outputs something like

---
$ neutron-server --version
%prog 11.el7ost
---

I'm guessing since Ied2acb37c366f1a45aed72b6b76f11e2de23828e when
oslo.config moved from optparse to argparse?

Change-Id: Ie51d2d1263a215390e106201b35902d6c401506d
Merge "Fix program name in --version output"