Fix a Net::DNS version quirk in the "resolver" system test

Net::DNS versions older than 0.68 insert a ./ANY RR into the QUESTION
section if the latter is empty.  Since the latest Net::DNS version
available with stock RHEL/CentOS 6 packages is 0.65 and we officially
support that operating system, bin/tests/system/resolver/ans8/ans.pl
should behave consistently for various Net::DNS versions.  Ensure that
by making handleUDP() return the query ID and flags generated by
Net::DNS with 8 zero bytes appended.

(cherry picked from commit 6c3c6aea)
7 jobs for 393-fix-a-net-dns-version-quirk-in-the-resolver-system-test-v9_11 in 6 minutes and 20 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Precheck
passed precheck:debian:sid:amd64 #23081
amd64 docker linux

00:00:10

 
  Build
passed build:debian:sid:amd64 #23082
amd64 docker linux

00:01:31

passed build:debian:sid:i386 #23083
i386 docker linux

00:01:34

 
  Test
passed systemtest:debian:sid:amd64 #23086
amd64 docker linux

00:04:23

passed systemtest:debian:sid:i386 #23087
i386 docker linux

00:04:34

passed unittest:debian:sid:amd64 #23084
amd64 docker linux

00:01:02

passed unittest:debian:sid:i386 #23085
i386 docker linux

00:00:55