Activity shows old preview in activity stream after new revision has been uploaded

This seems to happen all the time. Steps to reproduce:

1. Upload an image.
2. The activity should display that image
3. Upload a new version of the image
4. The "Uploaded new revision" activity shows the old preview

If I go ahead and update the description of the content item, an "updated content" activity gets generated, and shows the new preview, but the "uploaded new version" activity persists as being the old version.

The up-to-date preview status should be fetched on request in the activity, so it *should* be picking up the new revision in the "uploaded new version" activity.

This is reproduced in 0.2.0