NSFS | NC | fix versions_dir_cache validation

[nadavMiz]

Explain the changes

1. change versions_dir_cache validation to check if .versions dir exists before validation
2. change condition to account for all case of .version dir exists/ don't exists
3. enable relevant ceph tests

Issues: Fixed #xxx / Gap #xxx

1. https://github.com/noobaa/noobaa-core/issues/8314

Testing Instructions:

1. run ceph tests

• [ ] Doc added/updated
• [ ] Tests added