Add test for the proposed fix

Add test for the proposed fix

This test asserts that option "deny-answer-aliases" works correctly
when forwarding requests.

As a matter of example, the behavior expected for a forwarder BIND
instance, having an option such as deny-answer-aliases { "domain"; }
is that when forwarding a request for *.anything-but-domain, it is
expected that it will return SERVFAIL if any answer received has a CNAME
for "*.domain".