[tests] Disable reference-loader.exe test for now

The code it's supposed to test was temporarily disabled in 1bf9409629c144dc5400a800e8ab20ed516d5ced

mono/tests/Makefile.am

@@ -470,8 +470,7 @@ BASE_TEST_CS_SRC_UNIVERSAL=		\
 	bug-29585.cs	\
 	priority.cs	\
 	abort-cctor.cs	\
-	thread-native-exit.cs \
-	reference-loader.cs
+	thread-native-exit.cs
 
 if INSTALL_MOBILE_STATIC
 BASE_TEST_CS_SRC= \
@@ -693,6 +692,7 @@ DISABLED_TESTS=			\
 	bug-459094.exe \
 	delegate-invoke.exe \
 	bug-Xamarin-5278.exe \
+	reference-loader.cs \
 	$(PLATFORM_DISABLED_TESTS) \
 	$(EXTRA_DISABLED_TESTS) \
 	$(COOP_DISABLED_TESTS) \