Bugfix storage block get fails to provide data

- Fixes bug that was causing data not to be returned when retrieving a block through the storage block get end-point
  - block model needed to have the storage id told to it since there was no metadata storage id
  - adds a specific test for this scenario to the unit testing
- improves clarity in the storage drivers between block_id usages
Fixed - the metadata_storage_id was the correct one.