[3.15] Router currentURL Not Set

In Ember 3.12 the following code would report the current URL of the application:

```
class MyRoute extends Route {
@service router;

activate() {
super.activate(...arguments);
console.log('here you are:', this.router.currentURL);
}
}
```

In Ember 3.15 this will always report `null`. This is expected to work per [RouterService#currentURL](http://api.emberjs.com/ember/3.15/classes/RouterService/properties/currentURL?anchor=currentURL). Cursory investigation shows that both `currentRouteName` nor `currentRoute` are set either.

Curiously the `RouterService` reports the correct URL when used within a Component.

Sample application: https://github.com/jherdman/where-art-thou. Note that the console will always log a `null` URL, whereas the component correctly reports the URL.