I have no idea where the FRONTEND environment variable came from (I
think it's from my original write of Commento v1, which had whole bunch
of different terminologies).
Anyway, the `os.Getenv("FRONTEND")` would basically amount to nothing
all the time, and it would redirect to "/login" irrespective of whether
the user has a subdirectory-based COMMENTO_ORIGIN value.
Closes https://gitlab.com/commento/commento-ce/issues/72
