Allow to skip discovered mdevs

Currently there is no way to avoid auto-discovery of mdev devices.
The only way to avoid them propagating to nova.conf is through
the config override.

Change-Id: Ie1c40a427599e610278262cfdb55fdcf017d4ede

defaults/main.yml

@@ -580,6 +580,12 @@ nova_vendor_data_overrides: {}
 nova_api_metadata_uwsgi_ini_overrides: {}
 nova_api_os_compute_uwsgi_ini_overrides: {}
 
+# Attempt to auto-discover available vGPU devices.
+# It is recommended to define them explicitly through ``nova_enabled_mdev_types``.
+# Doing so has precedence over discovered ones and does not require to
+# disable the variable explicitly.
+nova_discover_mdev_types: true
+
 # Enabled vGPU Types - dict defining 'type' and 'address' (optional) of vGPU
 # an address is only required when supporting more than one physical GPU on the host
 # Example 1:

tasks/main.yml

@@ -119,8 +119,14 @@
   tags:
     - always
 
-- name: Importing nova_mdev_detect tasks
+- name: Including nova_mdev_detect tasks
-  ansible.builtin.import_tasks: nova_mdev_detect.yml
+  ansible.builtin.include_tasks: nova_mdev_detect.yml
+  args:
+    apply:
+      tags:
+        - always
+  when:
+    - nova_discover_mdev_types | bool
   tags:
     - always