fix squad error in squad-client test

```
test_malformed_data (tests.test_shortcuts.SubmitResultsShortcutTest) ... [ERROR] squad_client.core.models: Failed to submit results: There is already a test run with job_id 12345
ok
```

The error in question is output from `squad` when this test is run. Perhaps `squad` should be logging these errors or we should try and capture them in the test and output them as a failure?