Add stubs for UpdateEngine.CleanupSuccessfulUpdate

This API waits for merge to finish after rebooting to
the new Virtual A/B build.

Test: pass
Bug: 138808328
Change-Id: I9422f0ffb1876b71ab45e994fc2d5c76d9ec3a75
diff --git a/binder_service_android.cc b/binder_service_android.cc
index 214801b..c376f4e 100644
--- a/binder_service_android.cc
+++ b/binder_service_android.cc
@@ -214,7 +214,15 @@
           payload_metadata, str_headers, &error));
   if (error != nullptr)
     return ErrorPtrToStatus(error);
+  return Status::ok();
+}
 
+Status BinderUpdateEngineAndroidService::cleanupSuccessfulUpdate(
+    int32_t* return_value) {
+  brillo::ErrorPtr error;
+  *return_value = service_delegate_->CleanupSuccessfulUpdate(&error);
+  if (error != nullptr)
+    return ErrorPtrToStatus(error);
   return Status::ok();
 }