Here is what I did:
1) Fast traveled around my settlements looking for provisioners. When I found one I.....
a) reassigned them to food or defense. Then I "Moved" them to another settlement.
2) Repeated this until I could not find any more provisioners, active anywhere.
NOTE: They will retain the name "Provisioner" but show their new assignments (or unassigned if just moved)
3) Then I "Moved" one provisioner to each settlement. When this was done, I.......
4) Reassigned each provisioner to a route from their new "home" to the next closest settlement listed as an option for them when assigning them a trade route.
A little convoluted, I know, but it seemed like the best option, and it seems to have worked.
The trade route "ring" appears as you would expect. The people have not all visually shown up in their new homes yet, and the old routes have not disappeared yet either, but I am told that this may take a little time. I have been told that it takes time for them to travel, and for the abandoned routes to be seen as "broken."