Expose nameServers on dme_secondary_dns

[sebmck]

Right now the resource dme_secondary_dns doesn't return any additional attributes other than what it accepts which reduces it's usefulness. We are using a terraform integration with our registrar to automatically update nameservers and it would be nice if the resource also return the nameServers property that accompanies the dns/secondary API that's specified here:

{
  ...
"nameServers": [
    {
      "ipv6": "2600:1800:5::1",
      "ipv4": "208.94.148.13",
      "fqdn": "ns5.dnsmadeeasy.com",
      "groupId": 100,
      "id": 6
    },
    {
      "ipv6": "2600:1801:6::1",
      "ipv4": "208.80.124.13",
      "fqdn": "ns6.dnsmadeeasy.com",
      "groupId": 100,
      "id": 7
    },
    {
      "ipv6": "2600:1802:7::1",
      "ipv4": "208.80.126.13",
      "fqdn": "ns7.dnsmadeeasy.com",
      "groupId": 100,
      "id": 8
    }
  ]
  ...
}

Right now we have to manually go into the DME dashboard and hard code the variables.