In the cases where we test SOA serial updates and TTL updates, we check
if for "all zones loaded" to ensure the new zone content is loaded. But
this is the unsigned zone, the signed zone still needs to be produced.
There is thus a timing issue where the dig request comes in before
the signing process has finished.
Add a retry quiet to mitigate against it.
(cherry picked from commit 827bba05a0)
2174c566ff