Add a Net::DNS prereq for digdelv, fetchlimit, rpzrecurse, and zero

tests to avoid failed tests when Net::DNS is not present.
7 jobs for kchen/bind9-test-prereqs in 6 minutes and 7 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Precheck
passed #6857
docker linux
precheck:debian:sid:amd64

00:00:10

 
  Build
passed #6858
docker linux
build:debian:sid:amd64

00:01:22

passed #6859
docker linux
build:debian:sid:i386

00:01:28

 
  Test
passed #6862
docker linux
systemtest:debian:sid:amd64

00:04:27

passed #6863
docker linux
systemtest:debian:sid:i386

00:04:26

passed #6860
docker linux
unittest:debian:sid:amd64

00:00:35

passed #6861
docker linux
unittest:debian:sid:i386

00:00:35