title: hapi-auth-cookie not overwriting default tll
body: <p>I am using the plugin for an API REST using hapi 16.6.2 and hapi-auth-cookie 7.0.0. I set the keepAlive : true in the plugin initialization. In the login controller I have a "remember me" parameter which sets the ttl (request.cookieAuth.ttl) for 15 days. This is not posible as the keepAlive function overwrites with the default ttl. </p>
  
  <p>Code sample, you can use the example on the plugin page <a href="https://github.com/hapijs/hapi-auth-cookie/blob/v7.0.0/example/index.js" rel="nofollow noreferrer">https://github.com/hapijs/hapi-auth-cookie/blob/v7.0.0/example/index.js</a></p>
  
  <p>You just have to add keepAlive and ttl on plugin register</p>
  
  <pre><code>server.auth.strategy('session', 'cookie', true, {
      password: 'password-should-be-32-characters',
      cookie: 'sid-example',
      redirectTo: '/login',
      isSecure: false,
      keepAlive: true,
      ttl: 15 * 60 * 60 * 1000
             ...
  </code></pre>
  
  <p>and use the ttl method on the controller, i.e:</p>
  
  <pre><code>if (remember) {
  
      request.cookieAuth.ttl(15 * 24 * 60 * 60 * 1000); 
  
  }
  </code></pre>
  
  <p>If the remember me is checked by the user, set the cookie duration to 15 days. This will not be set, instead the default 15 min is used. ¿Am I missing something? ¿Is not the right approach for a remember me?</p>