BuildAPI: Create faux.empty_completed_unsuccessfully_error; use in Test service.

If this looks good, I can follow up with a broader CL to change remaining cases that should use faux.empty_completed_unsuccessfully_error

BUG=chromium:1029872
TEST=run_tests

Change-Id: Ifbe29f35a3bc5a9cb684d20511574b7829e12727
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1949419
Reviewed-by: Alex Klein <saklein@chromium.org>
Commit-Queue: Michael Mortensen <mmortensen@google.com>
Tested-by: Michael Mortensen <mmortensen@google.com>
diff --git a/api/controller/test.py b/api/controller/test.py
index 9ac83a9..6bbd03f 100644
--- a/api/controller/test.py
+++ b/api/controller/test.py
@@ -121,7 +121,8 @@
   deserialize_metrics_log(output_proto.events, prefix=build_target.name)
 
 
-@faux.all_empty
+@faux.empty_success
+@faux.empty_completed_unsuccessfully_error
 @validate.validation_complete
 def ChromiteUnitTest(_input_proto, _output_proto, _config):
   """Run the chromite unit tests."""