bundles/vnstat: add graph for "yesterday"

bundles/vnstat/metadata.py

@@ -35,6 +35,7 @@ def nginx_dashboard(metadata):
 
     return {
         'cron': {
+            'vnstat_yesterday_graph': '0 0 * * *    root    /usr/bin/vnstati --output "/var/www/vnstat/yesterday.png" --hours > /dev/null 2>/dev/null',
             'vnstat_generate_web_dashboard': '*/10 * * * *    root    /usr/local/bin/generate-vnstati /var/www/vnstat > /dev/null 2>/dev/null',
         },
         'nginx': {