*   Avoid namespacing routes inside engines.

    Mountable engines are namespaced by default so the generated routes
    were too while they should not.

    Fixes #14079.

    *Yves Senn*, *Carlos Antonio da Silva*, *Robin Dupret*

Please check [4-1-stable](https://github.com/rails/rails/blob/4-1-stable/railties/CHANGELOG.md) for previous changes.