[Sahara] Cannot create cluster in other tenant with enabled is_public

[Evgeny Sikachev]

ENVIRONMENT: MOS 9.0, ISO 363

STEPS TO REPRODUCE:
1. Create env with sahara
2. Deploy env with sahara
3. Create new tenant, user, role
4. Login as admin user
5. Mark cluster template as public
6. Login as other user
7. Create cluster with shared template

EXPECTED RESULT:
Cluster created

ACTUAL RESULT:
Error: Internal Server Error.
In sahara-api.log I can see http://paste.openstack.org/show/497851/

Re-creation of cluster with same name failed with "Error: Duplicate entry for object vanilla-d79213558acd40f6bd84494ed7193517. Failed on columns: ['name'] Error ID: ebcf7f0e-8ea3-4f70-94c9-e100118a0989" because cluster created in admin tenant