As per
https://www.icann.org/en/system/files/files/name-collision-mitigation-01aug14-en.pdf
prior to a new top-level domain being put into service there is a
controlled interuption service which will return explicit responses to DNS
A, MX, SRV, and TXT queries that can be used to detect private namespace collisions.
Modify the signature of copy_txt_to_realm() to accept a krb5_context so
that meaningful errors can be recorded.
Write a warning to the log (if any).
Change-Id: I51ff8feed4f9d2af8b956bd4ba26e1c4644247c2
b0e7dc5106