Fixed PHP-1109: upsert returns an array of ids rather then the _id
Merge pull request #704 from bjori/PHP-1109-upserted-id

Fixed PHP-1109: Upsert should return _id instead of array of ids

* bjori/PHP-1109-upserted-id:
  Fixed PHP-1109: upsert returns an array of ids rather then the _id
Merge remote-tracking branch 'upstream/v1.5'

* upstream/v1.5:
  Fixed PHP-1109: upsert returns an array of ids rather then the _id