[CI] Add extra metadata to windows node pool

This patch adds additional metadata to the windows node pool so that running
terraform apply does not force recreation of the node pool everytime, which
is reasonably expensive time wise.

premerge/main.tf

@@ -118,7 +118,12 @@ resource "google_container_node_pool" "llvm_premerge_windows" {
     # Windows Defender causes an increase in test times by approximately an
     # order of magnitude.
     metadata = {
-      "sysprep-specialize-script-ps1" : "Set-MpPreference -DisableRealtimeMonitoring $true"
+      "sysprep-specialize-script-ps1" = "Set-MpPreference -DisableRealtimeMonitoring $true"
+      # Terraform wants to recreate the node pool everytime whe running
+      # terraform apply unless we explicitly set this.
+      # TODO(boomanaiden154): Look into why terraform is doing this so we do
+      # not need this hack.
+      "disable-legacy-endpoints" = "true"
     }
     disk_size_gb = 200
   }