We previously had 'use image' as a default, but not 'create image', which is inconsistent and leads to unexpected failures.
There may be situations when Terraform/Ansible/etc. fail to provision test machines. In these cases, we want to fail fast instead of waiting until we time out in circle-test-pre and circle-test-smoke.
This should help speed-up the build by provisioning test VMs while we run unit tests, and destroying them while we generate coverage reports.
Marc CARRE