Add cloudstack_domain as a data source

[ianc769]

Adding cloudstack_domain as a data source:

data "cloudstack_domain" "foo" {
  filter {
    value = "name"
    name = "ROOT"
  }
}

output "domain_id" {
  value = data.cloudstack_domain.foo.id
}
output "domain_name" {
  value = data.cloudstack_domain.foo.name
}
output "network_domain" {
  value = data.cloudstack_domain.foo.network_domain
}
output "parent_domain_id" {
  value = data.cloudstack_domain.foo.parent_domain_id
}

data.cloudstack_domain.foo: Reading...
data.cloudstack_domain.foo: Read complete after 0s [id=65c9befb-1a1c-11f0-85c0-460f7764ea25]

Changes to Outputs:
  + domain_id        = "65c9befb-1a1c-11f0-85c0-460f7764ea25"
  + domain_name      = "ROOT"
  + network_domain   = ""
  + parent_domain_id = ""

You can apply this plan to save these new output values to the Terraform state, without changing any real infrastructure.