[JIRA] (OVIRT-2031) Use the systemd-nspawn mode for mock

Use the systemd-nspawn mode for mock ------------------------------------ Key: OVIRT-2031 URL: https://ovirt-jira.atlassian.net/browse/OVIRT-2031 Project: oVirt - virtualization made easy Issue Type: Improvement Components: mock_runner Reporter: Barak Korren Assignee: infra Labels: tracker Mock has long had the ability to use a full container via systemd-nspawn as opposed to a plain chroot. If we can leverage this, we can get many of the benefits of using containers without rebuilding our whole system on a new container backend. There were many issue in the past that prevented us from using that functionality. This ticket if for collecting tickets tracking these issues together.