Clea DuVall’s “Happiest Season” can be viewed as a radical holiday movie, in that it uses, hell mimics, the innumerable heterosexual Christmas movie cliches that came before it, but forges them through the lenses of a queer perspective. Yes, it’s the token emblem of your average holiday romantic comedy, but it’s the unadorned authentic touch brought forth by DuVall (“The Intervention”) that turns “Happiest Season” into a slightly likable affair.