Update oslo.log to 3.20.0
Update oslo.log to 3.20.0

Change-Id: I6ede1b9d82e614994f86c0685a5e359c2630184e
Depends-on: I1f4b49476e6a4bec9ab3ef9312dc490a22e9ff43

openstack/rpm-packaging,openstack/rpm-packaging