Rename oslo-config to oslo.config.

Change-Id: Ic6f17676ba597a055c89425ecd3c3164dfe30db2
Reviewed-on: https://review.openstack.org/24466
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins