Update oslo.privsep to 1.18.0
Update oslo.privsep to 1.18.0

Change-Id: I944c2dc8bcc8b17735c33351a140605f5c52b094
Depends-on: I1d21a9b232bf9a99a298098b2b22a58afd6dd13a
Depends-On: I885fe8aa4668ed64054d1d37384fd357b334049a

openstack/rpm-packaging,openstack/rpm-packaging