By Simon Lewis and David Brunnstrom WASHINGTON (Reuters) -British Foreign Secretary David Cameron and U.S. Secretary of State Antony Blinken said on Thursday they had discussed the “vital” U.S.-UK Indian Ocean air base at Diego Garcia, and Blinken said Washington recognized British sovereignty there. The air base is on British Indian Ocean Territory in the Chagos Islands that a vote in the United Nations General Assembly in 2019 said should be returned to Mauritius. Cameron did not give a specific response at a joint news conference with Blinken when asked about a report in Britain’s Daily Tel…