Fix logic of discovering hosts by service

For quite some time, we relate usage of --by-service flag for
nova-manage cell_v2 discover_hosts command to the used nova_virt_type.
However, we run db_post_setup tasks only once and delegating to the
conductor host. With latest changes to the logic, when this task in
included from the playbook level it makes even less sense, since
definition of nova_virt_type for conductor is weird and wrong.

Instead, we attempt to detect if ironic is in use by checking hostvars
of all compute nodes for that. It will include host_vars, group_vars,
all sort of extra variables, etc.

Thus, ironic hosts should be better discovered now with nova-manage
command.

Related-Bug: #2034583
Change-Id: I3deea859a4017ff96919290ba50cb375c0f960ea

defaults/main.yml

@@ -311,6 +311,7 @@ nova_console_type: "{{ (ansible_facts['architecture'] == 'aarch64') | ternary('s
 ## Nova ironic console
 # Set the console type. Presently the only options are ["serialconsole", "disabled"].
 nova_ironic_console_type: "disabled"
+nova_ironic_used: "{{ _nova_ironic_used }}"
 
 ## Nova console proxies
 # Set the console proxy types.

tasks/nova_db_post_setup.yml

@@ -22,7 +22,7 @@
 - name: Perform a cell_v2 discover
   command: >-
     {{ _db_nova_bin }}/nova-manage cell_v2 discover_hosts{{ (debug | bool) | ternary(' --verbose', '') }}{{
-      (nova_virt_type == 'ironic') | ternary(' --by-service', '') }}
+      (nova_ironic_used | bool) | ternary(' --by-service', '') }}
   become: yes
   become_user: "{{ _db_nova_system_user_name }}"
   changed_when: false

vars/main.yml

@@ -33,6 +33,15 @@ _nova_oslomsg_notify_vhost_conf: >-
     )
   }}
 
+_nova_ironic_used: |-
+  {% set _virt_types = [] %}
+  {% for hv in groups[nova_services['nova-compute']['group']] %}
+  {%   if 'nova_virt_type' in hostvars[hv] %}
+  {%     set _ = _virt_types.append(hostvars[hv]['nova_virt_type']) %}
+  {%   endif %}
+  {% endfor %}
+  {{ ('ironic' in _virt_types | unique) }}
+
 nova_venv_packages: |-
   {%- set pkg_list = nova_pip_packages | union(nova_user_pip_packages) %}
   {%- if nova_oslomsg_amqp1_enabled | bool %}