The shutdown system test sends queries when named is shutting down, not
in an attempt to get answers but to destabilize the server into a crash.
With isctest.query.udp() defaulting to try up to ten times with a
ten-second timeout to get a response we don't care about from a likely
terminated server, we make the test run much longer than needed because
of retries and long timeouts.
(cherry picked from commit 463ab2f3f5)
86c7bb4a0c