After a year of coronavirus lockdowns, the start of summer beckons with vacation plans made possible by relaxed COVID-19 restrictions. But a severe worker shortage brings a warning for travelers: Expect delays and pack a little patience. Lifeguards and hotel housekeepers are in short supply. So are rental cars. And don’t count on having a fruity cocktail at the hotel Tiki bar. The labor shortage is hitting the nation’s tourist destinations just as they try to rebound from a year lost to the pandemic. It threatens to derail the travel industry’s recovery even as many Americans are itching to get away again at last.