Add support check mode for all info modules

As it's required by new ansible-test rules.
See https://github.com/ansible-collections/overview/issues/45#issuecomment-893543025
Change-Id: Ib6b73e810b972997b8de2b4a9eb8e07e246823d5

plugins/modules/compute_flavor_info.py

@@ -174,7 +174,8 @@ class ComputeFlavorInfoModule(OpenStackModule):
             ['name', 'ram'],
             ['name', 'vcpus'],
             ['name', 'ephemeral']
-        ]
+        ],
+        supports_check_mode=True
     )
 
     deprecated_names = ('openstack.cloud.compute_flavor_facts')