chore: disable neutron coredns on ovn backend (#761)

diff --git a/roles/coredns/tasks/main.yml b/roles/coredns/tasks/main.yml
index c3fe1a2..3f1e942 100644
--- a/roles/coredns/tasks/main.yml
+++ b/roles/coredns/tasks/main.yml
@@ -38,6 +38,7 @@
 
 - name: Deploy Helm chart
   run_once: true
+  when: atmosphere_network_backend != 'ovn'
   kubernetes.core.helm:
     name: "{{ coredns_helm_release_name }}"
     chart_ref: "{{ coredns_helm_chart_ref }}"
diff --git a/roles/neutron/vars/main.yml b/roles/neutron/vars/main.yml
index 67fb2d3..3ccd02e 100644
--- a/roles/neutron/vars/main.yml
+++ b/roles/neutron/vars/main.yml
@@ -75,7 +75,6 @@
       DEFAULT:
         service_plugins: qos,ovn-router,segments,trunk
       ovn:
-        dns_servers: "{{ neutron_coredns_cluster_ip | default('10.96.0.20') }}"
         ovn_emit_need_to_frag: true
     ovn_metadata_agent:
       DEFAULT: