BOSTON – Sessions Harlan had never so much as gotten a public mention before Monday’s revelry at TD Garden, the night the Denver Nuggets clinched their first playoff berth since 2013. Denver’s cheerful security guard perked up, though, as Nuggets coach Michael Malone, tucked in a back hallway near the visitor’s locker room, explained what the milestone meant to him. “It’s a credit to our staff, players, security guards, training staff, everybody,” Malone said.