FILE PHOTO: Honorees Stevie Nicks and Lindsey Buckingham perform during the 2018 MusiCares Person of the Year show honoring Fleetwood Mac at Radio City Music Hall in Manhattan, New York, U.S., January 26, 2018. REUTERS/Andrew Kelly/File Photo LOS ANGELES (Reuters) – Former Fleetwood Mac guitarist Lindsey Buckingham underwent emergency open heart surgery last week that