Test that fake child delegation cannot overwrite parent's glue RR

Test that fake child delegation cannot overwrite parent's glue RR

In short, the attacker tries to spoof at least one answer that has the
following form:

    rcode NOERROR
    flags QR
    ;QUESTION
    trigger$RANDOM.victim. IN TXT
    ;ANSWER
    ;AUTHORITY
    trigger$RANDOM.victim. 3600 IN NS ns.victim.
    ;ADDITIONAL
    ns.victim. 3600 IN A 10.53.0.3

This attack was originally reported as "test case 2".

Co-authored-by: Michał Kępień <michal@isc.org>
(cherry picked from commit b5dc46fe6e0e8f05767377ae171c043ed72552d6)