hostname without container-id

[tofkamp]

When I create a new container, the hostname ends with the container number. Some people will find this handy, but it looks strange in the DNS, and other references. And proxmox knows the number already.
In the shape file there is a cloudinit line setting the hostname: "hostname: deb-lxc"
But the name is not deb-lxc but deb-lxc-109.
Where can I change the format of the hostname, so it won't add the container number ?