Created Unassigned: Runtime exception in unit-tests with synthetic controller [1429]

Hi,
After updating from 5.0.0-rc1 to 5.0.0 I started to get runtime exception in place where previously I didn't:

>The request context property on the request must be null or match ApiController.RequestContext.Result

Here's the code to create a "synthetic" controller:

```
public static T Create<T>(params object[] args) where T : ApiController
{
var config = new HttpConfiguration();

var request = new HttpRequestMessage();
request.SetRequestContext(new HttpRequestContext { IncludeErrorDetail = true });
request.SetConfiguration(config);

T controller = (T)Activator.CreateInstance(typeof(T), args);
controller.Request = request;
return controller;
}
```

But `controller.RequestContext` is read-only and `controller.RequestContext.Result` doesn't exist.