Upgrade oslo.config version to 1.4.0
Upgrade oslo.config version to 1.4.0

gate-solum-infra-guestagent-requirements was failing because
we were using oslo.config>=1.2.1

Change-Id: I59dae34a3d4d44ac9047a803a536ecf933246b85

openstack/solum-infra-guestagent,stackforge/solum-infra-guestagent