Comment 1 for bug 1957081

as WA, it seems to need manual action here
1. login inside docker container with mistral_api
2. install mistral-extra with pip
 # pip3 install mistral-extra
3. restart mistral_api container
4. populate actions using mapping file
#~ mistral-db-manage --config-file /etc/mistral/mistral.conf --openstack_actions_mapping_path /var/lib/kolla/venv/lib/python3.8/site-packages/mistral_extra/actions/openstack/mapping.json populate_actions
5. execute 'populate' action with the same parameters as in step 4.

In my case, installation of the mistral-extra package was required in all of the mistral_* containers (not sure it is necessary for all)
Here the simple script doing all work :)

##########
docker exec -itu root mistral_api pip3 install mistral-extra; \
docker exec -itu root mistral_engine pip3 install mistral-extra; \
docker exec -itu root mistral_executor pip3 install mistral-extra; \
docker exec -itu root mistral_event_engine pip3 install mistral-extra; \
docker restart mistral_api mistral_engine mistral_executor mistral_event_engine
sleep 10; \
docker exec -itu root mistral_api mistral-db-manage --config-file /etc/mistral/mistral.conf --openstack_actions_mapping_path /var/lib/kolla/venv/lib/python3.8/site-packages/mistral_extra/actions/openstack/mapping.json populate_actions; \
docker exec -itu root mistral_api mistral-db-manage --config-file /etc/mistral/mistral.conf --openstack_actions_mapping_path /var/lib/kolla/venv/lib/python3.8/site-packages/mistral_extra/actions/openstack/mapping.json populate
#########
After that our workflows starts to use openstac.actions like keystone.project_list etc..

Hope it will help.