Switch to oslo.config.
Switch to oslo.config.

The oslo-config package has been renamed. Switch to the new
version. (should fix SmokeStack).

Change-Id: I6a0fa803b0076bc5338c996e21bbcef54e1d75cd

zancas/hacking,openstack-dev/hacking,emonty/oslo-hacking,openstack-dev/hacking,hyakuhei/cleantox,zancas/hacking,emonty/oslo-hacking,hyakuhei/cleantox