Fix EZP-20539: Public API - Defaut editor permissions not working correctly

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This PR fixes EZP-20539: Public API - Defaut editor permissions not working correctly

This fixes the issue in currently possible way.
The problem is subtree limitation requiring Locations to check for access, and unpublished Content having no Locations before publishing. So the best guess is made if user should be allowed to edit content.

Better solution which would check permissions properly would involve the ability to load node assignements (or their parent locations), which subtree limitation could check.
This also involves the way Locations will be managed in SqlNg and future NoSQL storage.