fix: update the dnsconfig script to handle multiple interfaces (#24800)

e2e/terraform/packer/ubuntu-jammy-amd64/dnsconfig.sh

@@ -30,7 +30,7 @@ cp /tmp/resolv.conf /etc/resolv.conf
 
 # need to get the interface for dnsmasq config so that we can
 # accomodate both "predictable" and old-style interface names
-IFACE=$(ip route | grep default | awk '{print $5}')
+IFACE=$(ip route | grep default | awk '{print "interface="$5}')
 
 cat <<EOF > /tmp/dnsmasq
 port=53
@@ -38,7 +38,7 @@ resolv-file=/var/run/dnsmasq/resolv.conf
 bind-interfaces
 interface=docker0
 interface=lo
-interface=$IFACE
+$IFACE
 listen-address=127.0.0.1
 server=/consul/127.0.0.1#8600
 EOF