FIX: Fixed Versioned::get_version() to query the correct table which was...

... affecting lazy loaded fields

Cleaned up version of this pull request: https://github.com/silverstripe/sapphire/pull/1284

I looked at the 3.1 fix that was linked to [fbfff8d](https://github.com/silverstripe/sapphire/commit/fbfff8d) but I'm not convinced its the same fix. Whilst they may both have the same end result, this fix addresses the issue that Versioned::get_version() queries the wrong table (which in turn fixes the lazy loading issue).