ABUJA, Nigeria (AP) — Nigeria’s president on Friday replaced top security officials as the West African country grapples with unabated violence in the conflict-hit north and myriad security challenges. No reason was given but the shake-up comes as the government has denied rumors of a coup plot in the wake of local media reports that at least 20 military officers were arrested in September, including a brigadier general and a colonel. Nigeria’s capital, Abuja, was also shaken by protests this