CAIMITO, Cuba (Reuters) - They do not come to Cuba for the beaches and tropical mystique that draw more than 2 million other visitors each year. Instead they come to spend their vacations working in the countryside under a blazing sun, eating rice and beans and sharing a room without air-conditioning or toilet with seven others. They are so-called revolutionary tourists who arrive each year from about 50 countries for a "total immersion" in one of the world's few remaining socialist countries. "I call it a revolutionary vacation. I dedicate my free time to doing something concrete for the Cuban...