Update docker image version

bottin.hcl.example

@@ -12,7 +12,7 @@ job "directory" {
     task "server" {
       driver = "docker"
       config {
-        image = "lxpz/bottin_amd64:12"
+        image = "lxpz/bottin_amd64:13"
         readonly_rootfs = true
         port_map {
           ldap_port = 389