A man was struck and killed by a commuter rail train in Haverhill early yesterday, according to the Massachusetts Bay Transportation Authority. The victim was identified as Jeffrey Fraza, 34, who was pronounced dead at the scene, T spokeswoman Lydia Rivera said. Fraza had been a contestant on the boxing reality program “The Contender,’’ according to the show’s website. Rivera said Fraza was on the train right of way when he was hit at about 1:25 a.m. near Winter and Stevens streets. No passengers were on the train, which was Boston-bound after making its last service trip of the day, she said.