Fix tests for properties with default impls

... by properly forwarding the "standalone" flag in the newly added
collector.

src/Castle.Core/DynamicProxy/Contributors/InterfaceMembersWithDefaultImplementationCollector.cs

@@ -53,7 +53,7 @@ protected override MetaMethod GetMethodToGenerate(MethodInfo method, IProxyGener
 				return null;
 			}
 
-			return new MetaMethod(method, methodOnTarget, true, proxyable, !method.IsAbstract);
+			return new MetaMethod(method, methodOnTarget, isStandalone, proxyable, !method.IsAbstract);
 		}
 	}
 }