Fixed Proxy when using MultipartForm with byte[] (#473)

* wip

* ByteArrayContentHelper

* ByteArrayContentHelperTests

src/WireMock.Net/Owin/Mappers/OwinRequestMapper.cs

@@ -64,6 +64,7 @@ namespace WireMock.Owin.Mappers
                     ContentEncoding = contentEncodingHeader?.FirstOrDefault(),
                     DecompressGZipAndDeflate = !options.DisableRequestBodyDecompressing.GetValueOrDefault(false)
                 };
+
                 body = await BodyParser.Parse(bodyParserSettings);
             }