Sitcoms about dysfunctional families are old news, ditto for sitcom reboots, but what about a snarky meta-comedy about a dysfunctional TV cast? That’s the concept for Steven Levitan’s new show, “Reboot” about the revival of an early 2000s family sitcom “Step Right Up,” and despite being fictional, Levitan wanted the show at the center to feel as real as possible.