Stop NetworkManager from updating resolv.conf

cloud-init creates /etc/NetworkManager/conf.d/99-cloud-init.conf,
for NetworkManager to not update resolv.conf. However, subsequent
update of NetworkManager seems to remove that file as there is no
config(noreplace) directive for it. So after an update/upgrade of
overcloud nodes, reboot would cleanup the dns entries.

cloud-init do configuration only one time during first instance
boot. So this would ensure resolv.conf is not touched during
subsequent reboots.

Change-Id: I989e3f1d14fd33e97933032111cf48166dc5f50c

tripleo_ansible/roles/tripleo_bootstrap/tasks/main.yml

@@ -78,6 +78,25 @@
         name: "{{ tripleo_bootstrap_network_service }}"
         enabled: true
 
+- name: Stop NetworkManager from updating resolv.conf
+  become: true
+  when: tripleo_bootstrap_network_service == 'NetworkManager'
+  block:
+    - name: Set 'dns=none' in /etc/NetworkManager/NetworkManager.conf
+      ini_file:
+        path: /etc/NetworkManager/NetworkManager.conf
+        state: present
+        no_extra_spaces: true
+        section: main
+        option: dns
+        value: none
+        backup: true
+
+    - name: Reload NetworkManager
+      service:
+        name: NetworkManager
+        state: reloaded
+
 - name: Symlink puppet modules under /etc/puppet/modules
   become: true
   shell: >-