Add xen guest tools package to HASS OS

Tags: #<Tag:0x00007f3265fc23f0>

We already seem to ship VMWare’s open-vm-tools and the qemu agent with the operating system, it would be great if we could also add xen guest utilities. This would allow for a clean shutdown and better metrics when using xen based virtualization such as XCP-NG or Citrix Xen Server.

I guess a fix would look similar to this PR