Two police officers were in Haverhill District Court yesterday — not as prosecution witnesses, but as defendants in late-night fracas during which one off-duty officer Tasered the other. Lawrence Patrolman Daron Fraser was charged with domestic assault and battery and assault on a pregnant woman outside her home in Haverhill Tuesday night. Kingston NH Patrolman Joshua Wallar, who subdued Fraser with a Taser issued by his department, was charged with assault and battery with a dangerous weapon.