Add known hosts for all users

The role today only adds known hosts for the zuul user.
This replicates what d-g does today by adding a default known_hosts
file which applies to all users.

We csnnot remove the original task that adds for the zuul user since
there's a unit test in openstack-zuul-jons that expects that.

Depends-on: https://review.openstack.org/550425/

Change-Id: I54d4d975fa54cbb6df7dbed525211ab5c2cd6754

roles/multi-node-known-hosts/tasks/main.yaml

@@ -2,8 +2,16 @@
   generate_all_known_hosts:
     hostvars: "{{ hostvars }}"
 
-- name: add known_host record for every public key of every other ip, hostname
+- name: add known_host record for every public key of every other ip, hostname for ansible_user
   known_hosts:
     name: "{{ item.name }}"
     key: "{{ item.key }}"
   with_items: "{{ all_known_hosts }}"
+
+- name: add default known_host record for every user
+  become: true
+  known_hosts:
+    name: "{{ item.name }}"
+    key: "{{ item.key }}"
+    path: /etc/ssh/ssh_known_hosts
+  with_items: "{{ all_known_hosts }}"