HOUSTON — Austin Reaves couldn’t pinpoint exactly when it happened.  But he remembered what sparked the Lakers’ defensive turnaround , which has carried over for 3 ½ months, through their first-round playoff series victory over the Rockets, which ended with Friday’s 98-78 Game 6 victory at Toyota Center . The Lakers’ Deandre Ayton (5) and his teammates stymied the Rockets with their defensive intensity. NBAE via Getty Images Nearly midway through the regular season, the Lakers ranked 26th in defensive rating, performing even worse on the less glamorous end of the floor than even their biggest detractors expected entering the season. Only a few of the worst teams in the NBA (Kings, Pelicans, Wizards and Jazz) ranked worse than them defensively at the time.  The Lakers knew a change was needed, and it came during their 110-93 win over the Raptors on Jan. 18, when they started playing more zone defense than they had up to that point in the season.…