Job save callback should be called without arguments

If I call

jobs.createJob({...}).save(function (error) {
    if (error) {
        // Unable to save job
    } else {
       // Job saved!
    }  
});

The error in the callback is set to the job. It should be undefined. 

Ideally, we should be able to test both cases (job saved successfully / job save failed), but that's a new feature.
