Workaround for terraform lambda_multi_value_headers_enabled problem

As described in: hashicorp/terraform-provider-aws#7960

Terraform is saying:

    Terraform will perform the following actions:

      ~ module.upload-service.module.upload-service-database.aws_lb_target_group.pgbouncer
          lambda_multi_value_headers_enabled: "" => "false"

Installing the workaround described in the git issue.

terraform/modules/database/pgbouncer.tf

@@ -191,4 +191,7 @@ resource "aws_lb_target_group" "pgbouncer" {
   protocol    = "TCP"
   vpc_id      = "${var.vpc_id}"
   target_type = "ip"
+  lifecycle {
+     ignore_changes = "lambda_multi_value_headers_enabled"
+   }
 }