doc/howto/instances_create: improve LXD agent setup snippet

Signed-off-by: Simon Deziel <[email protected]>

doc/howto/instances_create.md

@@ -360,12 +360,13 @@ Now the VM can be rebooted, and it will boot from disk.
 If the VM installed from an ISO is a Linux distribution using `systemd`, it is possible to install the LXD agent inside of it. This can be done manually as the root user inside the VM:
 <!-- iso_vm_step8 end -->
 
-    mount -t 9p config /mnt
+    modprobe 9pnet_virtio
+    mount -t 9p config /mnt -o access=0,transport=virtio || mount -t virtiofs config /mnt
     cd /mnt
     ./install.sh
     cd /
     umount /mnt
-    systemctl start lxd-agent
+    reboot
 
 
 ````