Update a machine token when units are added to its containers

Fixes: https://bugs.launchpad.net/juju-gui/+bug/1342861

Adding units to a container should update the icons on a machine token.
`_updateMachineWithUnitData` updates the machine/container that is passed to it. In the case that the unit has been added to a container (not the root) we need to update both the container token and the parent machine token.