use actual system hostname in /etc/hosts templating

Author: sjpb

ansible/bootstrap.yml

@@ -14,7 +14,7 @@
       when: "'secrets_openhpc_' in (hostvars[inventory_hostname] | join)"
 
 - hosts: etc_hosts
-  gather_facts: false
+  gather_facts: yes
   tags: etc_hosts
   become: yes
   tasks:

ansible/roles/etc_hosts/README.md

@@ -1,6 +1,6 @@
 # etc_hosts
 
-Hosts in the `etc_hosts` groups have `/etc/hosts` created. The generated file defines all hosts in this group using `ansible_host` as the IP address and `inventory_hostname` as the canonical hostname. This may need overriding for multi-homed hosts. See `environments/common/inventory/group_vars/all/cloud_init.yml` for configuration.
+Hosts in the `etc_hosts` groups have `/etc/hosts` created. The generated file defines all hosts in this group using `ansible_host` as the IP address and `inventory_nodename` as the canonical hostname. This may need overriding for multi-homed hosts. See `environments/common/inventory/group_vars/all/cloud_init.yml` for configuration.
 
 # Variables:
 

ansible/roles/etc_hosts/templates/hosts.j2

@@ -1,6 +1,6 @@
 127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
 ::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
 
-{% for hostname in groups['etc_hosts'] | sort -%}
-{{ hostvars[hostname]['ansible_host'] }} {{ hostname }}
+{% for inventory_hostname in groups['etc_hosts'] | sort -%}
+{{ hostvars[inventory_hostname]['ansible_host'] }} {{ hostvars[inventory_hostname]['ansible_nodename'] }}
 {% endfor -%}