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
(cherry picked from commit 6881079d12a9fb2cf752a5f56116c1b4d3a7b75d)

roles/tripleo-bootstrap/tasks/main.yml

@@ -11,6 +11,30 @@
     rpm -q {{ item }}
   with_items: "{{ packages_bootstrap }}"
 
+- name: Populate service facts
+  service_facts:
+
+- name: Stop NetworkManager from updating resolv.conf
+  become: true
+  when:
+    - ansible_os_family | lower == 'redhat'
+    - ansible_distribution_major_version | int >= 7
+    - "'NetworkManager.service' in ansible_facts.services"
+    - ansible_facts.services['NetworkManager.service']['status'] == 'enabled'
+  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: Create /var/lib/heat-config/tripleo-config-download directory for deployment data
   file: