HAVANA (Reuters) - Russia will lease eight jets worth $650 million to its Cold War- era ally Cuba and will partially write off the country's multi-billion-dollar, Soviet-era debt under agreements signed during Prime Minister Dmitry Medvedev's visit to Havana on Thursday. Moscow will write off part of the $30 billion debt and will offer a 10-year refinancing plan for the remaining amount, according to the preliminary agreement, Russia's industry and trade minister Denis Manturov told reporters on the sidelines of the talks. ...