Fix OpenStack provider idempotency bugs

[ggiamarchi]

After the first apply some resources show a change on each subsequent apply although there's no change. This is caused by some computed fields not marked as computed.

For instance, the admin_state_up field for network resource is optional and the value is computed when not provided.

Considering the configuration

provider "openstack" {
}

resource "openstack_networking_network_v2" "web_net" {
    name = "web-net"
}

The first terraform apply do the job correctly but any subsequent apply show a change

$ terraform apply
openstack_networking_network_v2.web_net: Refreshing state... (ID: d5b20f32-b541-4895-998e-808ece5972be)
openstack_networking_network_v2.web_net: Modifying...
  admin_state_up: "true" => ""
openstack_networking_network_v2.web_net: Modifications complete

Apply complete! Resources: 0 added, 1 changed, 0 destroyed.

[aocole]

+1 Would really like to see this merged.

[phinze]

This LGTM - thank you!

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

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