BOSTON — Nickeil Alexander-Walker scored 21 points, Jalen Johnson had 19 points and 14 rebounds, and the Atlanta Hawks beat the Boston Celtics 117-106 on Wednesday night to avenge a lopsided home loss. Onyeka Okongwu added 17 points, Dyson Daniels had 15 and Corey Kispert 13 to help the Hawks win their fourth straight. They were locked in defensively, opening a 21-point lead late in the opening quarter on Alexander-Walker’s 3-pointer. AdvertisementThey held a 60-38 edge on Kispert’s 3 from the top in the second quarter before Boston closed the first half with an 8-0 spree. The Celtics made a few brief spurts in the second half but didn’t reduce their deficit below 12 points.