Kevin Spacey says he's NOT a sex addict ... but he claims a rehab center in Arizona wanted him to be one, so they could trot him out as a celeb spokesperson. The actor took the stand Tuesday in Santa Monica as part of a trial over the failed final season of "House of Cards" ... and he was asked about his time at The Meadows, a rehab facility in Arizona where he checked in following allegations of sexual harassment. Kevin testified he was initially told by a medical professional at the rehab