Change olso.config to be installed from pypi instead of tarballs.o.o

* For legacy reason, we pulled oslo.config from tarballs.o.o since
  that's where newer releases existed.  But pypi now has the
  versions we need.

Closes-Bug: #1334891
Change-Id: Ic366f47bfa771eba18bb6b3a7694b1edd9aed177