Restore the previous dry run behaviour

The way test submission works changed significantly when we switched to using the lava_runner. In that change set, I preserved the logic around when the submit tasks ran, such that they only ran when a valid LAVA configuration existed in the job variables, and when the pipeline is not for a merge request.

In repository preceding those changes, there was a valid LAVA configuration, but the test submission was given --dry-run so that we would run our templating, but stop short of submitting the jobs, even though we required a valid LAVA configuration to exist.

In the repository after these changes, there is not a valid LAVA configuration (since the required variables changed) and now the test generation step is no longer occurring on pipelines. Moreover, if we made the LAVA configuration valid for the state we have now, it would both generate and run the tests, because the generation and run steps have identical rules governing them in CI.

Therefore, remove the checks for a valid LAVA configuration from the generation step. This means we do not need a valid LAVA configuration in order to get the same behaviour we had before: generate the tests, but do not submit them.