fix(netbox_prefix): attributes are not properly read

[jeansebastienh]

Hi,

After importing the resources, terraform plan want to update prefix, status and tags altough there are already set on netbox.

$ terraform import netbox_prefix.ip_10_47_3_0 2                                                                                                                               
netbox_prefix.ip_10_47_3_0: Importing from ID "2"...                                                                                                                                                                                          
netbox_prefix.ip_10_47_3_0: Import prepared!                                                                                                                                                                                                  
  Prepared netbox_prefix for import                                                                                                                                                                                                           
netbox_prefix.ip_10_47_3_0: Refreshing state... [id=2]                                                                                                                                                                                        
                                                                                                                                                                                                                                              
Import successful!                                                                                                                                                                                                                            
                                                                                                                                                                                                                                              
The resources that were imported are shown above. These resources are now in your Terraform state and will henceforth be managed by Terraform.
$ terraform plan
...
netbox_prefix.ip_10_47_3_0: Refreshing state... [id=2]
...

Terraform will perform the following actions:

  # netbox_prefix.ip_10_47_3_0 will be updated in-place
  ~ resource "netbox_prefix" "ip_10_47_3_0" {
      + description = "srr1dc2-is-gw-adm-vip"
        id          = "2"
      + prefix      = "10.47.3.0/24"
      + status      = "active"
      + tags        = [
          + "prefix_mobility_fabric",
        ]
        # (1 unchanged attribute hidden)

Expected plan should be empty.

[fbreckle]

I wasnt even aware that the prefix resource was missing tests. Thank you very much!