api: test: Finish dropping BuildTargetUnitTest unit_tests.tar support

Drop remnants of support for generating unit_tests.tar in the
TestService/BuildTargetUnitTest endpoint.

BUG=b:217211026
TEST=run_tests

Change-Id: I33975a1df8050b983d9c935d7feb679c1f1b422d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/3661369
Tested-by: Alex Klein <saklein@chromium.org>
Commit-Queue: Alex Klein <saklein@chromium.org>
Reviewed-by: Lizzy Presland <zland@google.com>
diff --git a/api/controller/test.py b/api/controller/test.py
index 9ea33f3..dc85cd4 100644
--- a/api/controller/test.py
+++ b/api/controller/test.py
@@ -67,12 +67,6 @@
     return controller.RETURN_CODE_COMPLETED_UNSUCCESSFULLY
 
 
-def _BuildTargetUnitTestResponse(input_proto, output_proto, _config):
-  """Add tarball path to a successful response."""
-  output_proto.tarball_path = os.path.join(input_proto.result_path,
-                                           'unit_tests.tar')
-
-
 def _BuildTargetUnitTestFailedResponse(_input_proto, output_proto, _config):
   """Add failed packages to a failed response."""
   packages = ['foo/bar', 'cat/pkg']
@@ -85,7 +79,7 @@
     failed_pkg_data_msg.log_path.path = '/path/to/%s/log' % pkg
 
 
-@faux.success(_BuildTargetUnitTestResponse)
+@faux.empty_success
 @faux.error(_BuildTargetUnitTestFailedResponse)
 @validate.require_each('packages', ['category', 'package_name'])
 @validate.validation_complete