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/api/controller/board_build_dependency.py b/api/controller/board_build_dependency.py
index e150bc4..ea2e123 100644
--- a/api/controller/board_build_dependency.py
+++ b/api/controller/board_build_dependency.py
@@ -11,7 +11,7 @@
 
 from __future__ import print_function
 
-from chromite.api.gen import depgraph_pb2
+from chromite.api.gen.chromite.api import depgraph_pb2
 from chromite.lib import portage_util
 from chromite.service import dependency
 
diff --git a/api/controller/image.py b/api/controller/image.py
index 046b875..c734d99 100644
--- a/api/controller/image.py
+++ b/api/controller/image.py
@@ -12,7 +12,7 @@
 
 import os
 
-from chromite.api.gen import image_pb2
+from chromite.api.gen.chromite.api import image_pb2
 from chromite.lib import constants
 from chromite.lib import image_lib
 from chromite.service import image
diff --git a/api/controller/image_unittest.py b/api/controller/image_unittest.py
index d47a3bb..824b9bf 100644
--- a/api/controller/image_unittest.py
+++ b/api/controller/image_unittest.py
@@ -10,7 +10,7 @@
 import mock
 import os
 
-from chromite.api.gen import image_pb2
+from chromite.api.gen.chromite.api import image_pb2
 from chromite.api.controller import image as image_controller
 from chromite.lib import constants
 from chromite.lib import cros_test_lib
diff --git a/api/controller/sdk_unittest.py b/api/controller/sdk_unittest.py
index 7492b26..7774e0a 100644
--- a/api/controller/sdk_unittest.py
+++ b/api/controller/sdk_unittest.py
@@ -10,7 +10,7 @@
 from chromite.lib import cros_test_lib
 
 from chromite.api.controller import sdk as sdk_controller
-from chromite.api.gen import sdk_pb2
+from chromite.api.gen.chromite.api import sdk_pb2
 from chromite.lib import cros_build_lib
 from chromite.service import sdk as sdk_service
 
diff --git a/api/controller/test_archive_unittest.py b/api/controller/test_archive_unittest.py
index 9c73b8c..9c2f2af 100644
--- a/api/controller/test_archive_unittest.py
+++ b/api/controller/test_archive_unittest.py
@@ -10,7 +10,7 @@
 import os
 
 from chromite.api.controller import test_archive as test_archive_controller
-from chromite.api.gen import test_archive_pb2
+from chromite.api.gen.chromite.api import test_archive_pb2
 from chromite.lib import cros_build_lib
 from chromite.lib import cros_test_lib
 from chromite.lib import osutils