Convert some chain shell-based system tests in python

Convert some chain shell-based system tests in python

Rewriting a couple of shell-based chain system test into python. Those
tests exercise the dname resolution of either an authoritative or
resolver without extra queries (it is self resolver either because the
target is in an authoritative zone or in the same authoritative answer).

Also add an extra test checking the same mechanism, this time, from the
resolver cache (no resolver involed).

Those highlight the fact that `query_dname()` can be called in situation
where the query type is DNAME, and even though, it needs to be resolved.