Ensure trusted proxies are set before calling Request::isSecure()

From what I can tell the reverse_proxy settings are not wired up yet. Attached is a patch that uses them in DrupalKernel::initializeRequestGlobals().

It is just adding the small snippet below:

      // Initialize proxy settings.
      if (Settings::get('reverse_proxy', FALSE)) {
        $proxies = Settings::get('reverse_proxy_addresses', array());
        if (count($proxies) > 0) {
          Request::setTrustedProxies($proxies);
        }
      }