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".

(cherry picked from commit 9bdb960a16a69997b08746e698b6b02c8dc6c795)

bin/tests/system/forward/ns5/rebind.db

@@ -0,0 +1,13 @@
+$TTL    86400
+@       IN      SOA     rebind. admin.rebind. (
+                              1         ; Serial
+                         604800         ; Refresh
+                          86400         ; Retry
+                        2419200         ; Expire
+                          86400 )       ; Negative Cache TTL
+
+@           IN    NS    ns
+
+ns          IN    A     10.53.0.5
+
+subdomain   IN    A     10.53.0.1