Fix a missing initialization
diff --git a/test/cpp/end2end/server_builder_plugin_test.cc b/test/cpp/end2end/server_builder_plugin_test.cc
index 87e3709..58d56b2 100644
--- a/test/cpp/end2end/server_builder_plugin_test.cc
+++ b/test/cpp/end2end/server_builder_plugin_test.cc
@@ -61,6 +61,7 @@
     init_server_is_called_ = false;
     finish_is_called_ = false;
     change_arguments_is_called_ = false;
+    register_service_ = false;
   }
 
   grpc::string name() GRPC_OVERRIDE { return PLUGIN_NAME; }