Modify saveCurrentSettings behavior to create rdefs (See #12145)

After an extended discussion this morning, we decided to change
the saveCurrentSettings method to internally call saveAsNew if
the rdef does not belong to the current user.

The previous behavior was causing 5.0.1 clients to fail (4 tests
this morning were red.) The only sacrifices that had to be made
were:

 * thumbnails couldn't be generated at the same time, and
 * *intentional* saving as another user is no longer supported.