Target Group is not updated nor is it destroyed

Terraform Version

0.10.2

Terraform Configuration Files

port was changed from 1234:

resource "aws_alb_target_group" "alb-tg" {
  depends_on = ["module.database"]
  name     = "${var.environment_name}-test"
  port     = 4321
  protocol = "HTTP"
  vpc_id   = "${var.vpcid}"
 health_check {
   healthy_threshold   = "3"
   interval            = "30"
   matcher             = "200"
   path                = "/metadata"
   port                = "4321"
   protocol            = "HTTP"
   timeout             = "5"
   unhealthy_threshold = "2"
 }
}

resource "aws_alb_listener_rule" "test_host_based_routing" {
  listener_arn = "${var.alb_listener_arn}"
  priority     = 86

  action {
    type             = "forward"
    target_group_arn = "${aws_alb_target_group.alb-tg.arn}"
  }

  condition {
    field  = "host-header"
    values = ["test-api.${var.environment_name}.${var.subdomain}"]
  }
}

Expected Behavior

Terraform should be able to change the listener port for an existing target group. Or at least, delete the target group and create a new one with the new rules.

Actual Behavior

Error applying plan:

1 error(s) occurred:

* module.chat.aws_alb_target_group.alb-tg: 1 error(s) occurred:

* aws_alb_target_group.alb-tg: Error creating ALB Target Group: DuplicateTargetGroupName: A target group with the same name 'vpc-test' exists, but with different settings
	status code: 400, request id: 45238941-9cc0-11e7-a060-674673373add

Steps to Reproduce

1. create a VPC with a target group listening on port 1234
2. change the port listener in HCL code to 4321
3. Terraform can't apply the change

[hashibot]

This issue has been automatically migrated to hashicorp/terraform-provider-aws#1711 because it looks like an issue with that provider. If you believe this is not an issue with the provider, please reply to this issue and let us know.

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