set expect 100 continue for post requests

MediaBrowser.Common.Implementations/HttpClientManager/HttpClientManager.cs

@@ -64,6 +64,9 @@ namespace MediaBrowser.Common.Implementations.HttpClientManager
             _logger = logger;
             _fileSystem = fileSystem;
             _appPaths = appPaths;
+
+            // http://stackoverflow.com/questions/566437/http-post-returns-the-error-417-expectation-failed-c
+            ServicePointManager.Expect100Continue = false;
         }
 
         /// <summary>