By Alessandra Prentice ZAPORIZHZHIA, Ukraine (Reuters) – A convoy of buses carrying evacuees from southeastern Ukraine, including some 40 civilians who had been holed up in the Azovstal steel plant in besieged Mariupol, arrived on Sunday in the Ukrainian-controlled city of Zaporizhzhia, a U.N. official said. Osnat Lubrani, the U.N. humanitarian coordinator for Ukraine, said eight buses had arrived in the city. About 40 of the 174 evacuees on board had been rescued from the steel plant. Lubrani said in a statement that the evacuations brought to more than 600 the number of people evacuated from…