CleanupInstanceStuffsJob, CleanupOrphanedPreviewContainersJob, and
CheckMissingDatabaseBackupsJob had no uniqueFor. A lock left by a
stopped worker blocked them for up to 24 hours.
- Set uniqueFor to 60, 600, and 1800 seconds
- Give CheckMissingDatabaseBackupsJob a 1800 second timeout, so a run
cannot outlive its lock
