did not handle privatelink acr well

when testing against private endpoint ACR
https://docs.microsoft.com/en-us/azure/container-registry/container-registry-private-link

have following output:
Canonical name for ACR (abc.azurecr.io): abc.privatelink.azurecr.io.
[2021-01-28T17:09:44Z] ACR location: privatelink
ACR location 'privatelink' does not match your cluster location 'eastus2'. This may result in slow image pulls and extra cost.

Start with the private-link ACR example and the Azure Private Link documentation linked in the report. Trace the logic that derives the ACR location and compares it with the cluster location, then determine the expected handling for the `privatelink` hostname. Done means the diagnostic no longer reports an incorrect location mismatch for this setup.

Written by the indexing model from the issue text.