By Trevor Hunnicutt and Miguel Gomes LUANDA (Reuters) -Joe Biden pledged lasting U.S. engagement with Africa on Africans’ own terms as he met his Angolan counterpart Joao Lourenco in Luanda on Tuesday as part of his only visit to sub-Saharan Africa as U.S. president. Fulfilling a pledge to visit the continent during his term in office, which ends in January, Biden said the United States was…