Allow to skip volume type management by role

Right now it is not possible to avoid creation of a default volume type
which will have the same name as a backend. In case operator want to
rename volume type or have a different name - it will not be possible
as of today.

While we should migrate to using openstack_resources role for managing
of QoS and volume_types [1], the patch/modules are not ready and will
not be backportable anyway.

[1] https://review.opendev.org/c/openstack/openstack-ansible-plugins/+/906372

Change-Id: Ic1e190fc86bd3b6fd2cc771273e28b5bb095a322

defaults/main.yml

@@ -310,6 +310,8 @@ cinder_quota_backup_gigabytes: 1000
 #       - lvm_high_iops
 #       - lvm_low_iops
 
+cinder_manage_volume_types: True
+
 # Override generated device filter in lvm.conf
 # Example:
 # cinder_lvm_devices_filter_override:

releasenotes/notes/allow_to_skip_volume_types-8698ec60660a0510.yaml

@@ -0,0 +1,5 @@
+---
+features:
+  - |
+    Added variable ``cinder_manage_volume_types`` that allows to skip volume
+    type creation and management by os_cinder role.

tasks/main.yml

@@ -260,10 +260,15 @@
     - cinder-config
 
 - name: Importing cinder_backends tasks
-  import_tasks: cinder_backends.yml
+  include_tasks: cinder_backends.yml
+  args:
+    apply:
+      tags:
+        - cinder-config
   when:
     - "groups[cinder_services['cinder-volume']['group']] | length > 0"
     - "_cinder_is_last_play_host"
+    - cinder_manage_volume_types | bool
   tags:
     - cinder-config