Merge branch '6858-incorrect-root-directive-after-snippet-application-in-ispconfig-3-3-beta-1' into 'develop'

Resolve "Incorrect root directive after snippet application in ISPConfig 3.3 Beta 1"

Closes #6858

See merge request ispconfig/ispconfig3!2010

Author: Till Brehm

server/plugins-available/nginx_plugin.inc.php

@@ -3170,7 +3170,7 @@ private function nginx_merge_locations($vhost_conf) {
                 $app->log('Token ##subroot is unsecure (server ID: '.$conf['server_id'].').', LOGLEVEL_WARN);
             } else {
                 $insert_pos = strpos($vhost_conf, ';', strpos($vhost_conf, 'root '));
-                $vhost_conf = substr_replace($vhost_conf, ltrim($subroot[1], '/'), $insert_pos, 0);
+                $vhost_conf = substr_replace($vhost_conf, '/'.ltrim($subroot[1], '/'), $insert_pos, 0);
             }
         }