{AKS} Fix live test race condition in ACNS preserve-settings test

Add aks wait + sleep between sequential updates in
test_aks_update_acns_preserves_existing_settings to avoid 409
OperationNotAllowed from an in-progress PutExtensionAddonHandler.
Remove the broken recording that captured the 409 response; needs
re-recording from a passing live run.

Signed-off-by: Quang Nguyen <nguyenquang@microsoft.com>

Author: nddq