Stopped apps should not renew certificates

We had a case where a stopped/ununsed app was generating cert renewal
errors.

One idea might be to suppress the notification as well.

src/reverseproxy.js

@@ -582,6 +582,8 @@ function renewCerts(options, auditSource, progressCallback, callback) {
 
         // add app main
         allApps.forEach(function (app) {
+            if (app.runState === apps.RSTATE_STOPPED) return; // do not renew certs of stopped apps
+
             appDomains.push({ domain: app.domain, fqdn: app.fqdn, type: 'main', app: app, nginxConfigFilename: path.join(paths.NGINX_APPCONFIG_DIR, app.id + '.conf') });
 
             app.alternateDomains.forEach(function (alternateDomain) {