build_target_util: Rename to build_target_lib.

Nitty name change. The module contains a class and is in lib, so
should be a _lib, not a _util.

BUG=chromium:1060351
TEST=run_tests

Change-Id: I539dc8e5288e71cc9408bc68861f20579ac70937
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2095746
Commit-Queue: Alex Klein <saklein@chromium.org>
Tested-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/api/controller/test.py b/api/controller/test.py
index 5a7ecdb..92af3b6 100644
--- a/api/controller/test.py
+++ b/api/controller/test.py
@@ -20,7 +20,7 @@
 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_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
@@ -102,7 +102,7 @@
   for package_info in blacklisted_package_info:
     blacklist.append(controller_util.PackageInfoToString(package_info))
 
-  build_target = build_target_util.BuildTarget(board)
+  build_target = build_target_lib.BuildTarget(board)
   chroot = controller_util.ParseChroot(input_proto.chroot)
 
   result = test.BuildTargetUnitTest(build_target, chroot, blacklist=blacklist,