Ignore controller user_data changes to allow plugin updates

* Updating the `terraform-provider-ct` plugin is known to produce
a `user_data` diff in all pre-existing clusters. Applying the
diff to pre-existing cluster destroys controller nodes
* Ignore changes to controller `user_data`. Once all managed
clusters use a release containing this change, it is possible
to update the `terraform-provider-ct` plugin (worker `user_data`
will still be modified)
* Changing the module `ref` for an existing cluster and
re-applying is still NOT supported (although this PR
would protect controllers from being destroyed)

azure/container-linux/kubernetes/controllers.tf

@@ -85,6 +85,7 @@ resource "azurerm_virtual_machine" "controllers" {
   lifecycle {
     ignore_changes = [
       "storage_os_disk",
+      "os_profile",
     ]
   }
 }