Fix machine token icon rendering issues

Placed token icons do not render properly under multiple situations. This fixes the following issues:

 - Switching away then back to mv fixes the machine token rendering issues but only renders the root container and unit.
 - Machine token doesn't get updated to show the units on deploy.
 - Root container doesn't get updated properly on deploy wrt placed units.

Persisting issues - These issues will not be resolved until a refactor of the token rendering code post 1.0:
- Container tokens disappear when deployed then reappear with the unit token properly rendered.
- Unit icons in the machine tokens disappear then reappear a few seconds later with the ack from juju.
So this reads something like that the owner of the tokens should be watching for change events on the db and updating tokens as required?