mDNS queries show dual IP address records on minimal mDNS when IP address changes

[jrhees-cae]

When using minimal mDNS, if IP address of network is changed, both the old and new IP address records will be returned in a query.

Eventually the 'old' IP address will be eliminated from the cache.

It appears that the old IP address is not being Removed.

[andy31415]

This is likely minMdns implementation not sending a 'clear cache' or 'leave' messages. We likely need to implement more of the mdns spec in minmdns.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[andy31415]

We are sending TTL=0 to clear cache since #19692. Assuming this one is fixed.