Folks Operetta revives a lost hit from pre-World War II Berlin. This operetta by composer Paul Abrahám and librettists Alfred Grünwald, Fritz Löhner-Beda, and Emmerich Földes (translated here by Gerald Frantzen) was a big hit in 1931 Berlin. The far-fetched story, set in Hawaii, then a U.S. territory, concerns a romantic triangle tinged with political tension.…