Remove `localhost` record from hosts file

After adding `localhost` to inventory explicitly [1] this caused an interesting
side-effect, where a record for `localhost` is being added to the managed block
in /etc/hosts file, which might override FQDN defenition for the host.

This also makes healthcheck-hosts.yml fail the test, since expected record is not present.

[1] https://review.opendev.org/c/openstack/openstack-ansible/+/899523

Change-Id: If1840530a54aa9ae22eda1d3094f0c40ab66ddde

releasenotes/notes/do_not_add_localhost_to_hosts-36e365b95dc9da42.yaml

@@ -0,0 +1,8 @@
+---
+fixes:
+  - |
+    After adding ``localhost`` to inventory explicitly this resulted in potential
+    FQDN change due to adding a record for localhost into managed block inside
+    ``/etc/hosts`` file.
+    This is now fixed and record for ``127.0.0.1`` will be removed from managed
+    by Ansible blocks inside /etc/hosts file.

tasks/openstack_update_hosts_file.yml

@@ -18,7 +18,9 @@
   set_fact:
     _etc_hosts_content: |-
       {% set records = openstack_host_custom_hosts_records %}
-      {% for item in groups['all'] %}
+      {% set _groups = groups['all'] %}
+      {% set _ = _groups.remove('localhost') %}
+      {% for item in _groups %}
       {%   set record = [] %}
       {%   set _target_rfc_name = item|replace('_', '-') %}
       {%   set _ans_hostname = hostvars[item]['ansible_facts']['hostname'] | default(_target_rfc_name) %}