`ModelMetadataType` chain followed further in MVC 6 than `MetadataType` chain in MVC 5

[dougbu]

For compatibility, should not check property types within a type found using [ModelMetadataType].

While confirming the behaviour for #2403, found MVC 6 actually finds more metadata (checks type chains further) than MVC 5. MVC 5 finds no validators with the following model:

    [MetadataType(typeof(MergedAttributesMetadata))]
    public class MergedAttributes
    {
        public PropertyType Property { get; set; }
    }

    public class MergedAttributesMetadata
    {
        public MetadataPropertyType Property { get; set; }
    }

    public class PropertyType
    {
    }

    [MetadataPropertyTypeValidator]
    public class MetadataPropertyType
    {
    }

In contrast, MVC 6 will find the MetadataPropertyTypeValidator. It should not.

[dougbu]

296ec77