By Polina Devitt, Gleb Stolyarov and Natalia Zinets MOSCOW/KYIV (Reuters) – Ukraine’s military has suspended commercial shipping at its ports after Russian forces invaded the country, an adviser to the Ukrainian president’s chief of staff said, stoking fear of supply disruption from the leading grain and oilseeds exporters. Russia earlier suspended the movement of commercial vessels in the Azov Sea until further notice, but kept Russian ports in the Black Sea open for navigation, its officials and five grain industry sources said on Thursday. Ukraine is a major exporter of corn (maize), much o…