NEW YORK (UPI)--Convicted skyjacker Rodolfo Rivera Rios, who was returned to the United States after seven years in a Cuban prison, Friday was sentenced to life imprisonment for commandeering a 747 jetliner to Havana in 1970.  Rios, 35, was sentenced by U.S. District Court Judge Thomas C. Platt, who also ordered psychiatric treatment for the Puerto Rican nationalist.