Add externaldns addon with CoreDNS support

Change-Id: If1ec70e59c328e350104585e70ec4a2231529929
diff --git a/metadata/service/common.yml b/metadata/service/common.yml
index 8b1052c..8c921db 100644
--- a/metadata/service/common.yml
+++ b/metadata/service/common.yml
@@ -46,6 +46,12 @@
           namespace: kube-system
           image: coredns/coredns:latest
           etcd_image: quay.io/coreos/etcd:v3.1.0
+        externaldns:
+          enabled: True
+          namespace: kube-system
+          image: mirantis/external-dns:latest
+          domain: ${_param:kubernetes_cluster_domain}
+          provider: coredns
         virtlet:
           enabled: False
           namespace: kube-system