Setting Cluster Ids on Virtual Networks not behaving correctly

[benosman]

When setting one or more specific cluster ids without the default cluster in the list (typically 0), the default cluster gets implicitly added.

Given the example:

resource "opennebula_virtual_network" "vnet" {
  name = "tarravnet"
  permissions = "660"
  group = "${opennebula_group.group.name}"
  bridge = "br0"
  physical_device = "eth0"
  type = "fw"
  mtu = 1500
  ar = [ {
    ar_type = "IP4",
    size = 16
    ip4 = "172.16.100.101"
  } ]
  dns = "172.16.100.1"
  gateway = "172.16.100.1"
  security_groups = [ 0 ]
  clusters = [100]
}

This will result in:

clusters        = [
  0,
  100,
]

The sunstone frontend also shows that this default cluster was added implicitly

I believe this is caused by the upstream virtual network controller in the api adding the default cluster automatically if none is specified:

https://github.com/OpenNebula/one/blob/master/src/oca/go/src/goca/virtualnetwork.go#L122-L130

Then this module just adds the list of clusters to the network after creation, without clearing the default first. Compounding this, it seems that this resource doesn't update the list of clusters after updating either, so the list is never checked.