LOS ANGELES (Reuters) – Grammy performers have been told to cover up at Sunday's big music awards show, and keep their buttocks, nipples and genitals under wraps. Their politics can't show either. In a "wardrobe advisory," broadcaster CBS also asked musicians and audience members likely to appear on camera at the February 10 Grammy Awards ceremony to avoid wearing brand names on T-shirts as well as clothing with political or activist slogans. "Please be sure that buttocks and female breasts are adequately covered. Thong type costumes are problematic. …