Mistral api returns 500 status code on "create execution" request in nonexistent workbook

[Sergey Murashov]

Steps to reproduce:
1. Send POST request to 'workbooks/{nonexistent workbook}/executions'

Actual result:
Mistral API returns 500 status code
ServerFault: Got server fault
Details: {"debuginfo": null, "faultcode": "Server", "faultstring": "Failed to create necessary DB objects: Workbook not found [workbook_name=nonexistentworkbook]"}

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/98736

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/98736
Committed: https://git.openstack.org/cgit/stackforge/mistral/commit/?id=9f2043e41e7c1c8a35331bc42ae93cbcd1e8b0e5
Submitter: Jenkins
Branch: master

commit 9f2043e41e7c1c8a35331bc42ae93cbcd1e8b0e5
Author: Nikolay Mahotkin <email address hidden>
Date: Mon Jun 9 14:37:13 2014 +0400

    Fix create execution when workbook does not exist

     * Controller return 404 Not Found if Workbook doesn't exist
       or workbook definition is empty (in case of empty
       Definition we can't start Execution)

    Closes-bug: #1325914

    Change-Id: I5ae18d378916c6eba81088603414300891f1b816