BAPI: Update service API to report LaCrOS version

The LaCrOS version is determined following the same approach used for
Chrome.

BUG=b:235371788
TEST=./unit_tests

Change-Id: I0a961c6f8fc7a6dd0d5cf510380c12f8473513c0
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/4205801
Tested-by: Gilberto Contreras <gcontreras@google.com>
Commit-Queue: Gilberto Contreras <gcontreras@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Alex Klein <saklein@chromium.org>
diff --git a/service/packages_unittest.py b/service/packages_unittest.py
index 41cf0f0..7819f41 100644
--- a/service/packages_unittest.py
+++ b/service/packages_unittest.py
@@ -1499,7 +1499,9 @@
             portage_util, "PortageqBestVisible", return_value=r1_cpv
         )
 
-        chrome_version = packages.determine_chrome_version(self.build_target)
+        chrome_version = packages.determine_package_version(
+            constants.CHROME_CP, self.build_target
+        )
         version_numbers = chrome_version.split(".")
         self.assertEqual(len(version_numbers), 4)
         self.assertEqual(int(version_numbers[0]), 78)
@@ -1512,7 +1514,9 @@
             "PortageqBestVisible",
             side_effect=cros_build_lib.RunCommandError("error"),
         )
-        target = packages.determine_chrome_version(self.build_target)
+        target = packages.determine_package_version(
+            constants.CHROME_CP, self.build_target
+        )
         self.assertEqual(target, None)