[csharp][generichost] Fix response testing when dataType missing #198

Job	Run time
Build .Net projects (samples/client/petstore/csharp/generichost/net4.7/AllOf)	1m 13s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.7/AnyOf)	2m 43s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.7/FormModels)	1m 16s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.8/AnyOfNoCompare)	1m 0s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.7/OneOf)	1m 4s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.7/UseDateTimeForDate)	1m 11s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.8/AllOf)	1m 13s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.8/AnyOf)	1m 7s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.7/AnyOfNoCompare)	1m 8s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.8/FormModels)	1m 9s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.7/Petstore)	1m 19s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.8/OneOf)	1m 10s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.8/UseDateTimeForDate)	1m 1s
Build .Net projects (samples/client/petstore/csharp/generichost/net4.8/Petstore)	1m 15s
	17m 49s

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