Currently the integration tests, when running in the CI, ignore at all the ephemeral payload pullspec referenced by the `release:latest` dep var.

This creates a disalignment between the iso image versions pointed by the current installer embedded metadata, and the one effectively retrieved during the test execution, producing different issues. In some cases this increases unnecessarily the execution times (for example, by forcing the verification of the downloaded cached images for every single test).

So, in general, it'd be recommended that the integration tests will use the current pullspec to ensure a more coherent/safer execution (and to improve also the overall timing).

Tech notes

• The CI job agent-integration-tests should inject the `release:latest` as `OPENSHIFT_INSTALL_RELEASE_IMAGE_OVERRIDE` (see for example here)
• The tests will have to use correct pull secret