Sharon Gless (“Cagney & Lacey”) has joined the cast of “Queer as Folk,” Showtime’s U.S. adaptation of the raunchy British series focusing on urban gay men and lesbians.Gless plays a waitress at a Pittsburgh diner who’s the mother of one of the lead male characters. Showtime has committed to 22 half-hours, having bought the franchise rights from Channel 4 Int’l. It’s a Tony Jonas Prods./Cowlip Prods. in association with Warner Bros. Jonas, Ron Cowen, Daniel Lipman and Richard Kramer are executive producers. The producer-writers are Jonathan Tolins and Jason Schafer. Russell T. Davies, the creator of the British series, will serve as a consultant. Russell Mulcahy is directing the two-hour premiere episode.