Liza Minnelli was in a self-deprecating mood at the Gramercy Park Hotel’s Rose Bar Monday night, where she was performing an intimate, invitation-only set to promote her new Decca CD, “Confessions,” reports The Post’s Frank Scheck. Holding up the disc that features a close-up photo of herself on the cover, the legendary diva asked the crowd, “Have you ever seen so much retouching? But I look swell. Sometimes I even fool myself into thinking that I really look like that!”