Chained tasks don't display correctly on-screen

[greiginsydney]

When copyNow completes and newThumbs fires, the on-screen status display returns to "Background tasks idle" instead of showing the status of the thumbnail creation. If the user presses F5 here, the page correctly detects the new/current task and the status updates correctly to show as the thumbs are created.

The intent is that the status should update automatically, reporting the copy process and then the thumbs creation count.