resolved: when the server feature level changes between query and response restart...

resolved: when the server feature level changes between query and response restart transaction

In some cases we learn something about a server's feature level through its responses. If we notice that after doing
basic checking of a response, and after collecting all auxiliary DNSSEC info the feature level of the server is lower
than where we started, restart the whole transaction.

This is useful to deal with servers that response rubbish when talked to with too high feature levels.