Making the network resource computable

This allows the obtained network information to be successfully stored
for environments that do not require a network resource to be specified.

builtin/providers/openstack/resource_openstack_compute_instance_v2.go

@@ -106,6 +106,7 @@ func resourceComputeInstanceV2() *schema.Resource {
 				Type:     schema.TypeList,
 				Optional: true,
 				ForceNew: true,
+				Computed: true,
 				Elem: &schema.Resource{
 					Schema: map[string]*schema.Schema{
 						"uuid": &schema.Schema{