At the moment, this ID is only included when using `Jobs().List()`, which returns `api.JobListStub`.
With this change, the ID will also be available when using `Jobs().Info()`, which returns `api.Job`.
In fact, `ParentID` is currently the only field present in `api.JobListStub` that is not part of `api.Job`.
Note: This has the side effect that `nomad run -output` will now include an empty `ParentID`.