Debug test_methoddispatch on Mono

[slide]

From @slide on March 14, 2017 15:48

Mono seems to put in a different value for [Optional] parameters than MS.NET, need to debug why and file a mono issue if necessary.

Copied from original issue: IronLanguages/main#1596

[slozier]

The failure is caused by the enums having multiple entries with the same value (e.g. EnumByte.Zero and EnumByte.MinByte are both 0). There's a similar failure with .NET 7 which changes the enum search order. In my opinion this is just an implementation detail and the test should probably avoid this ambiguity (or check for both cases).