Cron-trigger running failed when workflow's scope is updated to 'private' from 'public'

[Lingxian Kong]

steps to reproduce:

1. Tenant1 creates a 'public' workflow.
2. Tenant2 can see that workflow, and creates a cron-trigger using that workflow.
3. Tenant1 updates the scope of workflow from 'public' to 'private'.
4. Cron-trigger's execution fails, the error log:

2015-11-21 09:03:59.379 8645 ERROR mistral.engine.default_engine [-] Failed to start workflow 'simple_wf' id=None: Workflow not found [workflow_name=simple_wf]
Traceback (most recent call last):
  File "/vagrant/mistral/mistral/engine/default_engine.py", line 62, in start_workflow
    wf_def = db_api.get_workflow_definition(wf_name)
  File "/vagrant/mistral/mistral/db/v2/api.py", line 107, in get_workflow_definition
    return IMPL.get_workflow_definition(name)
  File "/vagrant/mistral/mistral/db/v2/sqlalchemy/api.py", line 255, in get_workflow_definition
    "Workflow not found [workflow_name=%s]" % name
NotFoundException: Workflow not found [workflow_name=simple_wf]

2015-11-21 09:03:59.384 8645 ERROR mistral.engine.default_engine [-] Cant fail workflow execution with id='None': not found.
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher [-] Exception during message handling: Workflow not found [workflow_name=simple_wf]
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher Traceback (most recent call last):
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/dispatcher.py", line 142, in _dispatch_and_reply
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher executor_callback))
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/dispatcher.py", line 186, in _dispatch
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher executor_callback)
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher File "/usr/local/lib/python2.7/dist-packages/oslo_messaging/rpc/dispatcher.py", line 129, in _do_dispatch
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher result = func(ctxt, **new_args)
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher File "/vagrant/mistral/mistral/engine/rpc.py", line 98, in start_workflow
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher **params
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher File "/vagrant/mistral/mistral/utils/__init__.py", line 112, in _logged
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher return func(*args, **kw)
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher File "/vagrant/mistral/mistral/engine/default_engine.py", line 105, in start_workflow
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher raise e
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher NotFoundException: Workflow not found [workflow_name=simple_wf]
2015-11-21 09:03:59.385 8645 ERROR oslo_messaging.rpc.dispatcher
2015-11-21 09:03:59.394 8645 ERROR oslo_messaging._drivers.common [-] Returning exception Workflow not found [workflow_name=simple_wf] to caller

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/252317

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/252317
Committed: https://git.openstack.org/cgit/openstack/mistral/commit/?id=3074df9f46ad35906fd7970d4bede8df77b3ec34
Submitter: Jenkins
Branch: master

commit 3074df9f46ad35906fd7970d4bede8df77b3ec34
Author: hparekh <email address hidden>
Date: Tue Jan 5 11:32:52 2016 +0900

    Disallow user to change workflow scope

    If workflow has any cron-trigger assoaciated
    outside of the workflow's tenant, user is
    not allowed to change its scope from 'public'
    to 'private'.

    Change-Id: I90bd903d46140af26a729d62176e079e02406eae
    Closes-bug: #1518655