Update Dockerfile
Update Dockerfile

change branch MASTER > v2.0-beta1
digitalocean/netbox,Alphalink/netbox,snazy2000/netbox,lampwins/netbox,digitalocean/netbox,digitalocean/netbox,snazy2000/netbox,Alphalink/netbox,lampwins/netbox,Alphalink/netbox,Alphalink/netbox,digitalocean/netbox,lampwins/netbox,snazy2000/netbox,lampwins/netbox,snazy2000/netbox