nginx-directory: fix description

Follow up fix for: grafana#1511

Signed-off-by: Oleg Zaytsev <mail@olegzaytsev.com>

Author: colega

nginx-directory/config.libsonnet

@@ -42,6 +42,10 @@
 
     // Allow for extra CSS to be injected.
     extra_css: '',
+
+    // Description shown below the title
+    description: '',
+    description_html: if self.description != '' then '<p class="description">%s</p>' % self.description else '',
   },
 
   _images+:: {

nginx-directory/directory.libsonnet

@@ -32,9 +32,6 @@ local link_data = import 'link_data.libsonnet';
       // For example proxy-pass of /grafana path will be passed as '%(path)s/grafana' to the upstream.
       normalized: true,
 
-      description: '',
-      description_html: if this._config.description != '' then '<p class="description">%s</p>' % this._config.description else '',
-
       // backwards compatible, service level config allows for more granular configuration
       read_timeout: this._config.nginx_proxy_read_timeout,
       send_timeout: this._config.nginx_proxy_send_timeout,