By Tom Balmforth, Max Hunder and Simon Lewis KYIV/KOSTYANTYNIVKA, Ukraine (Reuters) -Russia said on Sunday its forces had taken control of Ukraine’s eastern Luhansk region after capturing the final Ukrainian holdout of Lysychansk in heavy fighting, though Ukraine did not confirm the claim. Control of Luhansk, a key war aim for Russia, would come after weeks slow advances, hand Moscow a limited political win and shift the battlefield focus to neighbouring Donetsk region, where Ukraine still controls substantial territory. Driven back from the Ukrainian capital Kyiv following its Feb. 24 invasio…