Ignore commented hosts in the dev database.yml check

The single-db mode comments out the ci block, and the clone's setup_database_yml leaves CI's postgres host on those commented lines. The helper's leftover-host check matched them, so the new mode exited 1 on a real clone although its file was correct. The check now matches live host lines only, and the self-test runs the mode against a template with a commented ci block, which failed before the change.