Routesubscriber should set the config override language

This is only a partial fix, for some weird reasons, facet(s) (summaries) are gone when clearing the cache in a non default language.

It's possible the disappearing filters are an unrelated bug

Patch is against an older version (don't ask), but should be committed to latest as well against the latest - will try to reroll for latest diff.

The filter problem is something unrelated with our setup.

Against latest dev.