TIM COCKS WESTERN powers seeking to isolate Russia over Ukraine are disappointed at what they see as lukewarm support from African nations at the U.N. general assembly - where their 54 votes form a bloc large enough to swing resolutions. The Ukraine war comes at a time of heightened rivalry between the West, China and Russia over Africa's natural resources, trade and security ties. Below are some reasons for the continent's divided stance: HEARTS AND MINDS On the day of the invasion, February 24, the African Union unequivocally called on Russia to respect "the territorial integrity and national sovereignty of…