api/controller: Convert manual BuildTarget instantiations

There are controller_util functions to construct BuildTargets from
the protobuf messages so we can have a single place to address changes
to the protobuf message. Convert all the BuildTarget instantiations
from manual constructions to calls to the util function.

BUG=chromium:1060351
TEST=run_tests, cq

Change-Id: I60c6720cf7bbc60f122f2fa1e2e81ab13368193f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2096818
Reviewed-by: Michael Mortensen <mmortensen@google.com>
Commit-Queue: Alex Klein <saklein@chromium.org>
Tested-by: Alex Klein <saklein@chromium.org>
diff --git a/api/controller/test.py b/api/controller/test.py
index 92af3b6..ccaae00 100644
--- a/api/controller/test.py
+++ b/api/controller/test.py
@@ -20,7 +20,6 @@
 from chromite.api.controller import controller_util
 from chromite.api.gen.chromite.api import test_pb2
 from chromite.cbuildbot import goma_util
-from chromite.lib import build_target_lib
 from chromite.lib import constants
 from chromite.lib import cros_build_lib
 from chromite.lib import image_lib
@@ -88,7 +87,6 @@
 def BuildTargetUnitTest(input_proto, output_proto, _config):
   """Run a build target's ebuild unit tests."""
   # Required args.
-  board = input_proto.build_target.name
   result_path = input_proto.result_path
 
   # Method flags.
@@ -102,7 +100,7 @@
   for package_info in blacklisted_package_info:
     blacklist.append(controller_util.PackageInfoToString(package_info))
 
-  build_target = build_target_lib.BuildTarget(board)
+  build_target = controller_util.ParseBuildTarget(input_proto.build_target)
   chroot = controller_util.ParseChroot(input_proto.chroot)
 
   result = test.BuildTargetUnitTest(build_target, chroot, blacklist=blacklist,