WASHINGTON — Defense giant RTX last week announced CEO Greg Hayes will step down, and in his place will come Chris Calio, the company’s president and chief operating officer, who will take the top job in May. For the world’s second-largest defense contractor, analysts say, the change in leadership reflects a transition from an era of disruption to one of maintenance. Hayes oversaw the merger of Raytheon and United Technologies Corp. three years ago and the company’s rebranding as RTX this