cluster read should base check if ip of cluster is already connected

[Sczlog]

use cluster resource which already connected to server throw internal connect cluster error.

cloudtower_cluster.sample_cluster: Creating...
╷
│ Error: [POST /connect-cluster][500] connectClusterInternalServerError  &{Message:0xc0004ce720 OperationName:0xc0004ce6f0 Path:0xc0004ce6c0 Props:map[createCluster:map[code:CLUSTER_ALREADY_CONNECTED message:cluster already connected]] Stack:0xc0004ce750 Status:0xc00028afb0}
│ 
│   with cloudtower_cluster.sample_cluster,
│   on create.tf line 25, in resource "cloudtower_cluster" "sample_cluster":
│   25: resource "cloudtower_cluster" "sample_cluster" {
│ 
╵

[Sczlog]

temporary, terraform doesn't support mark one field as uniqueness

hashicorp/terraform-plugin-sdk#224

[Sczlog]

wait until terraofrm support global uniquesness detection