prefer_udp for upstream dns servers (#4810)

roles/kubernetes-apps/ansible/templates/coredns-config.yml.j2

@@ -23,9 +23,13 @@ data:
         }
         prometheus :9153
 {% if resolvconf_mode == 'host_resolvconf' and upstream_dns_servers is defined and upstream_dns_servers|length > 0 %}
-        forward . {{ upstream_dns_servers|join(' ') }}
+        forward . {{ upstream_dns_servers|join(' ') }} {
+          prefer_udp
+        }
 {% else %}
-        forward . /etc/resolv.conf
+        forward . /etc/resolv.conf {
+          prefer_udp
+        }
 {% endif %}
         cache 30
         loop