ADDIS ABABA — Rivals Sudan and South Sudan resumed security talks Thursday aimed at easing tensions on the disputed border, after they failed to reach a deal at negotiations last week. The African Union-mediated talks in the Ethiopian capital first began after South Sudan’s independence last July, but the latest rounds follow weeks of fighting in April that brought the two foes back to the brink of all-out war. This round of talks is expected to last two or three days.