OCPBUGS-32174: save correct bootstrap public IP

When the BYOIPv4 feature was introduced to the terraform provisioning in
50c0a9d, a new EIP resource was created unconditionally. The
bootstrap VM was first getting a public IP from the `associate_public_ip_address` config in the instance and that IP was
then discarded when the EIP was created and associated with the instance.

However, a "race" could happen in which, at the end of the bootstrap
stage, we saved the first (and now dead) IP address:
```
DEBUG Outputs:
DEBUG
DEBUG bootstrap_ip = "18.222.119.149"
DEBUG [INFO] running Terraform command: /c/terraform/bin/terraform output -no-color -json
DEBUG {
DEBUG   "bootstrap_ip": {
DEBUG     "sensitive": false,
DEBUG     "type": "string",
DEBUG     "value": "18.222.119.149"
DEBUG   }
DEBUG }
```
In case of bootstrap failure, the `gather bootstrap` would use the stale
IP address and fail to connect:
```
time="2024-04-12T15:08:49Z" level=info msg="Failed to gather bootstrap logs: failed to connect to the bootstrap machine: dial tcp 18.222.119.149:22: connect: connection timed out"
```
instead of using the actual EIP address "18.225.29.102".

This changes proposes the following fixes:

1. Only create an EIP if a public IPv4 pool has been specified.
2. Only `associate_public_ip_address` to the bootstrap instance if
   public IPv4 pools have *not* been specified.
3. At the end of the bootstrap stage, save the correct IP address by
   considering whether the bootstrap EIP was created or not.

Author: r4f4

data/data/aws/bootstrap/main.tf

@@ -161,7 +161,7 @@ resource "aws_instance" "bootstrap" {
   subnet_id                   = var.aws_publish_strategy == "External" ? var.public_subnet_ids[0] : var.private_subnet_ids[0]
   user_data                   = var.aws_bootstrap_stub_ignition
   vpc_security_group_ids      = [var.master_sg_id, aws_security_group.bootstrap.id]
-  associate_public_ip_address = local.public_endpoints
+  associate_public_ip_address = local.public_endpoints && var.aws_public_ipv4_pool == ""
 
   lifecycle {
     # Ignore changes in the AMI which force recreation of the resource. This
@@ -251,9 +251,10 @@ resource "aws_security_group_rule" "bootstrap_journald_gateway" {
 }
 
 resource "aws_eip" "bootstrap" {
+  count            = var.aws_public_ipv4_pool == "" ? 0 : 1
   domain           = "vpc"
   instance         = aws_instance.bootstrap.id
-  public_ipv4_pool = var.aws_public_ipv4_pool == "" ? null : var.aws_public_ipv4_pool
+  public_ipv4_pool = var.aws_public_ipv4_pool
 
   depends_on = [aws_instance.bootstrap]
-}
+}

data/data/aws/bootstrap/outputs.tf

@@ -1,3 +1,3 @@
 output "bootstrap_ip" {
-  value = local.public_endpoints ? aws_instance.bootstrap.public_ip : aws_instance.bootstrap.private_ip
+  value = var.aws_public_ipv4_pool != "" ? aws_eip.bootstrap[0].public_ip : local.public_endpoints ? aws_instance.bootstrap.public_ip : aws_instance.bootstrap.private_ip
 }