A petition to award Master-at-Arms 2nd Class Mark Mayo the Medal of Honor has appeared on the White House’s website, but a leading expert in military decorations says that’s not in the cards. Navy officials say Mayo was gunned down the night of March 24 while attempting to protect quarterdeck watch standers on the destroyer Mahan, after a man identified as 35-year-old truck driver Jeffrey Savage, an ex-convict, gained access to the pier and disarmed the ship’s petty officer of the watch. “He doesn’t qualify for the Medal of Honor because it wasn’t in combat,” said Doug Sterner, a Vietnam…