fix ambiguous reference

Author: ahgittin

camp/camp-brooklyn/src/main/java/org/apache/brooklyn/camp/yoml/BrooklynYomlTypeRegistry.java

@@ -209,7 +209,7 @@ public Maybe<Object> newInstanceMaybe(String typeName, Yoml yoml, @Nonnull Regis
                 // the create call will attach the loader of typeR
                 nextContext.loader(null);
 
-                return Maybe.of(registry().create(typeR, nextContext.build(), null));
+                return Maybe.of((Object) registry().create(typeR, nextContext.build(), null));
 
             } else {
                 // circular reference means load java, below