Fans of “Eastbound & Down” will be happy to know that “Vice Principals,” the new HBO comedy starring Danny McBride, promises the same type of debauchery. “Vice Principals,” however, is settling into the television trend of “short and sweet,” in other words — few seasons. “The whole series is only 18 episodes and that’s it. We just wanted to make a really long movie. It’s one school year and a complete story,” McBride said at the show’s premiere.