LUSAKA, Zambia – Tension is rising in Zambia ahead of presidential elections next week, prompting an unprecedented deployment of the military to clamp down on violence. The August 12 ballot is essentially a two-horse race between longstanding adversaries — President Edgar Lungu, 64, and Hakainde Hichilema, 59, who is making his sixth bid for the top job. Rival supporters wielding axes and machetes…