Commented Issue: DefaultBodyModelValidator should use ReferenceEqualityComparer for detecting cycles in object graphs [1024]

DefaultBodyModelValidator.ValidationContext.Visited is a HashSet<object> used to detect and avoid cycles in object graphs during validation. It uses Object equality rather than reference equality.

POSTED entities might be in an inconsistent state and hence their GetHashCode and Equals implementations might be incorrect.

Ideally, when we are doing cycle detecting, we should be checking for reference equality anyways.
Comments: [Fixed](https://aspnetwebstack.codeplex.com/SourceControl/changeset/1b19ae1e5ba4cb2057193b0081978800f176788f)