Fix unpacking syntax for Python 3.4

Python 3.5 introduced the ability to do unpacking before keyword
arguments, eg
```
my_method(**dictionary, foo=bar)
```

This was introduced in https://www.python.org/dev/peps/pep-0448/

This is not valid syntax in Python 3.4, which is what’s running on our
boxes.

This commit changes an instance of this syntax which was introduced in
56d9c29e91

app/statistics_utils.py

@@ -84,6 +84,6 @@ def get_failure_rate_for_job(job):
 
 def add_rate_to_jobs(jobs):
     return [dict(
-        **job,
-        failure_rate=(get_failure_rate_for_job(job)) * 100
+        failure_rate=(get_failure_rate_for_job(job)) * 100,
+        **job
     ) for job in jobs]