tests: Update mock to work with objstorage >= v2.0.0
_STORAGE_CLASSES will be renamed to OBJSTORAGE_IMPLEMENTATIONS.
Migrated from D8044 (view on Phabricator)
Staging instance, all changes can be removed at any time
_STORAGE_CLASSES will be renamed to OBJSTORAGE_IMPLEMENTATIONS.
Migrated from D8044 (view on Phabricator)