R1:dabd3f0b417b

Fix a race between Harbormaster and reviewers (often bots) to publish drafts for review

Summary:
See PHI309. There is a window of time between when all builds pass and when Harbormaster actually publishes a revision out of draft.

If any other user tries to interact with the revision during that window, they'll pick up the undraft transaction as a side effect. However, they won't have permission to apply it and will be stopped by a validation error.

Instead, only automatically publish a revision if the…