Don’t assume jobs status will be present

The API response for jobs includes a field called `job_status`. The API
response for uploads doesn’t.

The `Job` mode handles uploads and jobs, so it needs to account for the
possibility of the field not being there.

app/models/job.py

@@ -34,7 +34,7 @@ class Job(JSONModel):
 
     @property
     def status(self):
-        return self.job_status
+        return self._dict.get('job_status')
 
     @property
     def cancelled(self):