InRequestScope does not work in WCF Service Application

```
//does not work
Bind<IUnitOfWork>().To<UnitOfWork>().InRequestScope();

//works fine
Bind<IUnitOfWork>().To<UnitOfWork>().InScope(context => HttpContext.Current);
```

> Version:
> Ninject 3.2.2.0
> Ninject.Extensions.Wcf 3.2.1.0
> Ninject.Web.Common 3.2.2.0
