LOS ANGELES (Reuters) – A previously unknown audio tape of an interview with slain civil rights leader Martin Luther King Jr. was discovered recently in the attic of a Tennessee home, and a New York collector who bought the recording says he plans to offer it for sale next week. The 10-minute reel-to-reel recording was made on December 21, 1960, nearly three years before King’s famed “I Have a Dream” speech and more than seven years before he was gunned down in Memphis, Tennessee, collector Keya Morgan told Reuters on Thursday. …