Ensure /etc/resolv.conf content for CoreOS

Use cloud-init config to replace /etc/resolv.conf with the
content for kubelet to properly configure hostnet pods.

Do not use systemd-resolved yet, see
https://coreos.com/os/docs/latest/configuring-dns.html
"Only nss-aware applications can take advantage of the
systemd-resolved cache. Notably, this means that statically
linked Go programs and programs running within Docker/rkt
will use /etc/resolv.conf only, and will not use the
systemd-resolve cache."

Signed-off-by: Bogdan Dobrelya <bdobrelia@mirantis.com>

roles/dnsmasq/tasks/resolvconf.yml

@@ -9,6 +9,16 @@
   set_fact:
     resolvconffile: >-
       {%- if resolvconf.rc == 0 -%}/etc/resolvconf/resolv.conf.d/head{%- else -%}/etc/resolv.conf{%- endif -%}
+  when: ansible_os_family != "CoreOS"
+
+- name: target temporary resolvconf cloud init file
+  set_fact:
+    resolvconffile: /tmp/resolveconf_cloud_init_conf
+  when: ansible_os_family == "CoreOS"
+
+- name: create temporary resolveconf cloud init file
+  command: cp -f /etc/resolv.conf "{{ resolvconffile }}"
+  when: ansible_os_family == "CoreOS"
 
 - name: generate search domains to resolvconf
   set_fact:
@@ -100,3 +110,17 @@
   copy: src=dhclient_nodnsupdate dest=/etc/dhcp/dhclient.d/nodnsupdate mode=u+x
   notify: Dnsmasq | restart network
   when: ansible_os_family == "RedHat"
+
+- name: get temporary resolveconf cloud init file content
+  command: cat {{ resolvconffile }}
+  register: cloud_config
+  when: ansible_os_family == "CoreOS"
+
+- name: persist resolvconf cloud init file
+  template:
+    dest: "{{resolveconf_cloud_init_conf}}"
+    src: resolvconf.j2
+    owner: root
+    mode: 0644
+  notify: Dnsmasq | update resolvconf for CoreOS
+  when: ansible_os_family == "CoreOS"