AKS: Fix default nodepool upgrade settings

[caiovbraga]

2068

PR Checklist

---

• I have added example(s) inside the [./examples/] folder
• I have added the example(s) to the integration test list for normal (~30 minutes) or long runner >30 minutes
• I have checked the coding conventions as per the wiki
• I have checked to ensure there aren't other open Pull Requests for the same update/change?

Description

The current module has a bug if values for upgrade_settings are set

│ Error: Unsupported attribute
│ 
│   on .terraform/modules/caf/modules/compute/aks/aks.tf line 80, in resource "azurerm_kubernetes_cluster" "aks":
│   80:         max_surge = upgrade_settings.value.max_surge
│     ├────────────────
│     │ upgrade_settings.value is 1
│ 
│ Can't access attributes on a primitive-typed value (number).

I'm also adding the optional settings in the upgrade_settings block

Does this introduce a breaking change

• YES
• NO

Testing

[arnaudlh]

LGTM