artifacts: Add latest/ to image dir.

TEST=./run_tests
BUG=chromium:949566

Change-Id: I86b78b04da9a7a8f47dffa74179495157fad1e44
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1559153
Tested-by: Evan Hernandez <evanhernandez@chromium.org>
Reviewed-by: Jason Clinton <jclinton@chromium.org>
Reviewed-by: Sean Abraham <seanabraham@chromium.org>
diff --git a/api/controller/artifacts_unittest.py b/api/controller/artifacts_unittest.py
index 83773da..7a3f23e 100644
--- a/api/controller/artifacts_unittest.py
+++ b/api/controller/artifacts_unittest.py
@@ -130,7 +130,8 @@
     osutils.SafeMakedirs(self.archive_root)
 
     self.target = 'target'
-    self.image_root = os.path.join(self.source_root, 'src/build/images/target')
+    self.image_root = os.path.join(self.source_root,
+                                   'src/build/images/target/latest')
 
     self.input_proto = artifacts_pb2.BundleRequest()
     self.input_proto.build_target.name = self.target