Two small changes:

1) Bugfix for SimCloud. Now the host_resource_update method is called even
when the actual placement is determined by an external engine (communicated
back to CB through the pubsub mechanism).

2) The AI/VApp specific attribute "sut" is now propagated to the VMs. Useful
in case an external placement engine needs to make decisions for all VMs
that belong to a given AI/VApp.