owner_confirm_hex.go: fix login redirect typo
owner_confirm_hex.go: fix login redirect typo

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

adtac/commento,adtac/commento,adtac/commento,adtac/commento