title: GAE Webapp2 - destroying session doesn't work
body: <p>Or do I misunderstand how destroying work? Here's an example code:</p>
  
  <pre><code>class TestHandler(BaseHandler):
      def get(self):
          counter = self.session.get('counter')
          if not counter:
              counter = 0
          counter += 1
  
          if counter &gt; 5:
              self.auth.unset_session()
          else:
              self.session['counter'] = counter
  
          return self.response.write ( counter )
  </code></pre>
  
  <p>Session works, the counter counts, but either session isn't destroyed or destroying it doesn't null the value?</p>
  
  <p>Does destroying null only some values like userid and sessionid or do I completely miss the point? Thanks.</p>