Create a zone that triggers DNAME owner name checks in a zone that
is only reachable using a dual stack server. The answer contains
a name that is higher in the tree than the query name.
e.g.
foo.v4only.net. CNAME v4only.net.
v4only.net. A 10.0.0.1
ns4 is serving the test zone (ipv4-only)
ns6 is the root server for this test (dual stacked)
ns7 is acting as the dual stack server (dual stacked)
ns9 is the server under test (ipv6-only)
(cherry picked from commit f946133ec9)
726aa21913