[BUG][CSHARP][GENERICHOST] Write enum values in expected JSON format #211

Job	Run time
Build .Net projects (samples/client/petstore/csharp/generichost/net4.7/AllOf)	1m 21s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.7/AnyOf)	1m 11s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.7/OneOf)	1m 12s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.7/Petstore)	1m 9s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.7/FormModels)	1m 19s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare)	1m 39s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.8/AllOf)	1m 6s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate)	1m 3s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate)	1m 6s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.8/FormModels)	1m 40s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.8/AnyOf)	1m 8s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.8/Petstore)	1m 9s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.8/OneOf)	1m 10s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare)	1m 10s
	17m 23s

Provide feedback