Update to getGenericTypeOfReturnType

To be able to get the generic type of the List for methods such as:
<T extends Interface1> List<T> getList();
For complicated and very rare cases such as: <T extends Interface1, Interface2,Interface3> List<T> getList();
it would just return the first interface Interface1 and not the other two.

src/main/java/com/ericsson/commonlibrary/proxy/Util.java

@@ -468,6 +468,8 @@ private static Class<?> getGenericTypeOfReturnType(Method method, Type type) {
             return (Class<?>) wildType.getUpperBounds()[0];
         } else if (type instanceof ParameterizedType) {
             return ((Class) ((ParameterizedType) type).getRawType());
+        } else if (type instanceof TypeVariable) {
+            return (Class) ((TypeVariable) type).getBounds()[0]; //ignore the others, (typically only one anyway)
         }
         throw new IllegalArgumentException(
                 "Was not able to figure out the generic type of method: " + method.getName());