Use a standardized "FAILURE" mark when a job fails

We're skipping the actual message because doing that only adds newlines
into the mix, and that's bad™ for readability on Gerrit's web interface.
diff --git a/turbo_hipster/lib/models.py b/turbo_hipster/lib/models.py
index 78c599a..56bebd5 100644
--- a/turbo_hipster/lib/models.py
+++ b/turbo_hipster/lib/models.py
@@ -198,7 +198,7 @@
         if self.success:
             self.work_data['result'] = 'SUCCESS'
         else:
-            self.work_data['result'] = '\n'.join(self.messages)
+            self.work_data['result'] = 'FAILURE'
         self.job.sendWorkData(json.dumps(self._get_work_data()))
 
     def _send_final_results(self):