Mistral should returns 404 in the case of an absent execution's tasks request

[Vasudeo Nimbekar]

Mistral GET execution's tasks API returns 200 response status code and empty tasks response for absent execution id.

To reproduce:

- Execute GET request for v2/executions/{execution-id}/tasks API by passing absent execution-id.

Ex:
request:
GET http://mistral-host/v2/executions/00000000-0000-0000-0000-000000000000/tasks

response:
status code - 200
response data - {"tasks": []}

expected response:
status code - 404
response data -
{
    "faultcode": "Client",
    "faultstring": "WorkflowExecution not found [id=00000000-0000-0000-0000-000000000000]",
    "debuginfo": null
}

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/c/openstack/mistral/+/865985
Committed: https://opendev.org/openstack/mistral/commit/87c08ff42172c9fe7735777c98d07ec32c4cd179
Submitter: "Zuul (22348)"
Branch: master

commit 87c08ff42172c9fe7735777c98d07ec32c4cd179
Author: Vasudeo Nimbekar <email address hidden>
Date: Tue Nov 29 18:16:56 2022 +0530

    Update get execution's tasks functionality

    After this patch, it will validate execution-id exists in the DB while fetching tasks for the execution-id So, GET /v2/executions/execution_id/tasks API will return 404 for absent execution id.

    Closes-Bug: #1998210
    Change-Id: I6ac05f4b87c470a68cd67f19d1bd95a4d6cebe59

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/mistral 16.0.0.0b1 development milestone.