Build API: Update imports to new generated proto

BUG=chromium:940582, b:128456793
TEST=run_tests

Change-Id: I34645640bf4fa07b4403f9e2e5e596b7a59dff97
Reviewed-on: https://chromium-review.googlesource.com/1525076
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Tested-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Lann Martin <lannm@chromium.org>
diff --git a/scripts/build_api.py b/scripts/build_api.py
index c016993..9119133 100644
--- a/scripts/build_api.py
+++ b/scripts/build_api.py
@@ -13,11 +13,11 @@
 from google.protobuf import symbol_database
 
 from chromite.api import controller
-from chromite.api.gen import build_api_pb2
-from chromite.api.gen import depgraph_pb2
-from chromite.api.gen import image_pb2
-from chromite.api.gen import sdk_pb2
-from chromite.api.gen import test_archive_pb2
+from chromite.api.gen.chromite.api import build_api_pb2
+from chromite.api.gen.chromite.api import depgraph_pb2
+from chromite.api.gen.chromite.api import image_pb2
+from chromite.api.gen.chromite.api import sdk_pb2
+from chromite.api.gen.chromite.api import test_archive_pb2
 from chromite.lib import commandline
 from chromite.lib import cros_build_lib
 from chromite.lib import osutils