face: introduce NullTransport and use it in several places

Refs: #4528
Change-Id: Icc7a77232bca1a700ce1319493c15a85d05d7488
diff --git a/core/common.hpp b/core/common.hpp
index c918724..efc9856 100644
--- a/core/common.hpp
+++ b/core/common.hpp
@@ -33,12 +33,14 @@
 #define PUBLIC_WITH_TESTS_ELSE_PROTECTED public
 #define PUBLIC_WITH_TESTS_ELSE_PRIVATE public
 #define PROTECTED_WITH_TESTS_ELSE_PRIVATE protected
+#define OVERRIDE_WITH_TESTS_ELSE_FINAL override
 #define FINAL_UNLESS_WITH_TESTS
 #else
 #define VIRTUAL_WITH_TESTS
 #define PUBLIC_WITH_TESTS_ELSE_PROTECTED protected
 #define PUBLIC_WITH_TESTS_ELSE_PRIVATE private
 #define PROTECTED_WITH_TESTS_ELSE_PRIVATE private
+#define OVERRIDE_WITH_TESTS_ELSE_FINAL final
 #define FINAL_UNLESS_WITH_TESTS final
 #endif