[BUG] Binding to JObject doesn't work correctly in Service Bus extension

[JoshLove-msft]

When creating a function that binds to a JObject, if the received message does not have a contentType of application/json, a stackoverflow occurs - apparently due to the DataContractBinarySerializer getting confused. A simple fix would be to reorder the operations listed here, so that we do the Json conversion attempt before the XML attempt. Or we could check the typeof(TElement) and special case JObject to preserve the existing behavior as much as possible.