Update oslo.utils to 3.20.0
Update oslo.utils to 3.20.0

Change-Id: I48e895e71f43d5cc300066513b590d42038df107
Depends-on: I9e2c8cd5d7440dc88142ce1f0b5e6175f7bbe8c3

openstack/rpm-packaging,openstack/rpm-packaging