Fix Firewall Update

[zliang-akamai]

📝 Description

• Correct a checking logic during update
• Add UseStateForUnknown to prevent unexpected removals of Linode and NodeBalancers from a firewall.

✔️ How to Test

Automated Testing

make int-test PKG_NAME="linode/firewall"

Manual Testing

Verify any rule change won't detach the Linode from the firewall.

resource "linode_firewall_device" "my_device" {
  firewall_id = linode_firewall.my_firewall.id
  entity_id = linode_instance.my_instance.id
}

resource "linode_firewall" "my_firewall" {
  label = "my_firewall"

  inbound {
    label    = "http"
    action = "DROP"
    protocol  = "TCP"
    ports     = "80"
    ipv4 = ["0.0.0.0/0"]
    ipv6 = ["::/0"]
  }

  inbound_policy = "DROP"
  outbound_policy = "ACCEPT"
}

resource "linode_instance" "my_instance" {
  label      = "my_instance"
  region     = "us-southeast"
  type       = "g6-standard-1"
}

[lgarber-akamai]

@zliang-akamai Thanks for the quick turnaround on this! Could this PR be repointed to main so we can release it in a patch?

[zliang-akamai]

@lgarber-akamai the base has been changed to main, thanks for the review!

[lgarber-akamai]

Looks like the integration tests are required to merge to main but aren't run by default because this isn't the dev branch 👀