Clean up container cache prep in tests
Clean up container cache prep in tests

This patch cleans up the container cache preparation in the tests
due to the following patches:

- https://review.openstack.org/307856 (new image build process)
- https://review.openstack.org/315114 (new apt config process)
- https://review.openstack.org/322188 (new resolver config process)

Change-Id: Id267ce54dfb69f4ee70220bd55d9f07bd6b00648

os-cloud/openstack-ansible-galera_server,openstack/openstack-ansible-galera_server,os-cloud/openstack-ansible-galera_server,openstack/openstack-ansible-galera_server