WESTFIELD — A week before Adam Mason was to stand trial in district court for two counts of indecent assault and battery on a person under the age of 14, he pleaded guilty to two counts of assault and battery, according to court records.After pleading guilty to the lesser charges, Mason, 20, of Falcon Drive in Westfield, was sentenced to one year of administrative supervision probation by District Court Judge Tina Cafaro, according to court reco…