Query SRV records

[smhmhmd]

Issue #, if available:
Use SRV records to query for Microsoft Active Directory as per https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/verify-srv-dns-records-have-been-created#method-3-use-nslookup
Description of changes:

See these in the logs:
Found ldap._tcp.dc._msdcs DNS controller ip-aaaaa.contoso.com
Found ldap._tcp.dc._msdcs DNS controller ip-bbbbb.contoso.com

Testing done:
Tested domain-joined and domainless (opensource mode)

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