The change avoids the compiler CLI internal API from mismatching the following case as lazy loading
```
import { NonLazyLoadedModule } from './non-lazy-loaded/non-lazy-loaded.module';
export function getNonLazyLoadedModule() { return NonLazyLoadedModule; }
export const routes = [
{ path: '/some-path', loadChildren: getNonLazyLoadedModule }
];
```
The output of the check is later passed to `RouteDef.fromString()`, so, it makes sense to be only a string.
Fixesangular/angular-cli#3204
This change adds Compiler CLI support for any level of nesting for lazy routes.
For example `{app-root}/lazy-loaded-module-1/lazy-loaded-module-2/lazy-loaded-module-3`
Where `lazy-loaded-module-3` is lazy loaded from `lazy-loaded-module-2`,
and `lazy-loaded-module-2` is lazy loaded from module `lazy-loaded-module-1`,
and `lazy-loaded-module-1` is lazy loaded from `AppModule`
Fixesangular/angular-cli#3663
