support gather_facts: false; support setup-snapshot.yml

Some users use `gather_facts: false` in their playbooks.  This changes
the role to work in that case, by gathering only the facts it requires
to run.
CI testing can be sped up by creating a snapshot image pre-installed
with packages.  tests/setup-snapshot.yml can be used by a CI system
to do this.

Logging role tests used to check installed packages are necessary and
sufficient. Also, they uninstalled the installed packages at the end
of each test. They are eliminated since it'd get broken when the pre-
installed snapshot image is used.

- Remove the unnecessary setup task from tests_include_vars_from_parent.yml.

- Run set_vars.yml in the roles/rsyslog/tasks level via the logging role.

- To gather the all package names to be installed in tests/setup-
  snapshot.yml, set __snapshot_gather_vars to true.

- Improved the way how to get the packages to be installed then install
  them using the info. (using varnames lookup)

- tests/setup-snapshot.yml needs to gather the necessary ansible facts
  and the packages to be used in the series of tests. The task is done
  using the logging role where only gathering but no other tasks is
  executed.

- In ovirt/set_vars.yml, replacing default_ipv4 with network since gather_
  subset only takes allowed keywords.

defaults/main.yml

@@ -89,3 +89,11 @@ logging_files_template_format: ""
 # Output forward format
 # Allowed values: "traditional", "syslog",  or "modern"; default to "modern"
 logging_forwards_template_format: ""
+
+# ansible_facts required by the role
+__logging_required_facts:
+  - distribution
+  - distribution_major_version
+  - distribution_version
+  - os_family
+  - default_ipv4

roles/rsyslog/tasks/inputs/ovirt/main.yml

@@ -1,16 +1,7 @@
 ---
 # yamllint disable rule:line-length
-- name: Set platform/version specific variables
-  include_vars: "{{ item }}"
-  loop:
-    - "{{ role_path }}/vars/inputs/ovirt/default.yml"
-    - "{{ role_path }}/vars/inputs/ovirt/{{ ansible_facts['os_family'] }}.yml"
-    - "{{ role_path }}/vars/inputs/ovirt/{{ ansible_facts['distribution'] }}.yml"
-    - "{{ role_path }}/vars/inputs/ovirt/{{ ansible_facts['distribution'] }}_\
-      {{ ansible_facts['distribution_major_version'] }}.yml"
-    - "{{ role_path }}/vars/inputs/ovirt/{{ ansible_facts['distribution'] }}_\
-      {{ ansible_facts['distribution_version'] }}.yml"
-  when: item is file
+- name: Set ovirt platform/version specific variables
+  include_tasks: "{{ role_path }}/tasks/inputs/ovirt/set_vars.yml"
 
 # yamllint enable rule:line-length
 # Deploy configuration files

roles/rsyslog/tasks/inputs/ovirt/set_vars.yml

@@ -0,0 +1,23 @@
+---
+# SPDX-License-Identifier: GPL-3.0-only
+
+- name: Ensure ansible_facts used by role
+  setup:
+    gather_subset:
+      - min
+      - network
+  when: not ansible_facts.keys() | list |
+    intersect(__logging_required_facts) == __logging_required_facts
+
+- name: Set platform/version specific variables
+  include_vars: "{{ item }}"
+  loop:
+    - "{{ role_path }}/vars/inputs/ovirt/default.yml"
+    - "{{ role_path }}/vars/inputs/ovirt/{{ ansible_facts['os_family'] }}.yml"
+    - "{{ role_path }}/vars/inputs/ovirt/{{ ansible_facts['distribution'] }}.\
+      yml"
+    - "{{ role_path }}/vars/inputs/ovirt/{{ ansible_facts['distribution'] }}_\
+      {{ ansible_facts['distribution_major_version'] }}.yml"
+    - "{{ role_path }}/vars/inputs/ovirt/{{ ansible_facts['distribution'] }}_\
+      {{ ansible_facts['distribution_version'] }}.yml"
+  when: item is file