Check for private link DNS

[carlin-q-scott]

I tried using this tool but it failed at the DNS resolution step and did not help. It turned out the issue was the DNS server was providing a private link CNAME for my SQL Server public domain name, but there was no private link installed in my vnet. So I installed the private link service and the issue was resolved. I'm not entirely sure why that was necessary, but this script should have let me know that private link was configured but not installed.