Update oslo.privsep to 1.20.0
Update oslo.privsep to 1.20.0

Change-Id: Iaf6e36712842c2a293059a4bce81a3cadb0f50db
Depends-on: If0024c3943c8facd8007e9b64291a36500fb6041

openstack/rpm-packaging,openstack/rpm-packaging