Merle Haggard, George Strait  are among the first confirmed stars for this year’s post-ACM Awards concert special.  Lady Antebellum, The Band Perry and Carrie Underwood are also expected, while more artists are expected to be added to the lineup.  This year’s Academy of Country Music event is honoring the men and women in uniform.  “ACM Presents: An All-Star Salute to the Troops” will be taped at the MGM Grand Garden Arena in Las Vegas on April 7th — the day after the 49th annual ACM Awards.  The concert special will air on CBS on May 20th.