Set preferred_cloud_contract as true (required, to generate initial payment)
  there are only a single packing list generated as the API usage packacking lists are gone.

The computation of the API usage is been removed. There is no reason to invoice the API usage anymore.

The consumption should be based on computer resource consumption or by time based subscriptions.

Monitor Scope is used to define if an Hosting Subscription and/or Computer is monitored or not.

  The API that notify availability and building from Computer Partition is unecessary and it's
  implementation overuse resources and cause flaky effect on the state of the Computer Partition.

  At the Software Release, the states can be available/building/error, and this state tens to be
  immutable once the software release is finished (it will be available, where building and error are
  transitory states).

  At Computer Partition, we intent to have started/stopped/destroyed instances, where available and
  building were transitory, but they have no practical function as a second report would come quickly
  after. So we may consider that started is actually same as available, in this case, it is a duplicated
  meaning, as you cannot be available w/o been started/stopped.

  computer_partition.building were never used, as the master knew that a partition is been processed,
  so this API were never used.

  Report transitory states are prevent us to determinate the actuall state, considering that the latest
  actuall state is more relevant (started/stopped/destroyed).

This allow the person responsable on for support, load all monitoring URLs from all instances to that may contain a failure.

Stop or Destroyed instances don't required checks.

This cause a lot of headeache during the tests.

/reviewed-on nexedi/slapos.core!48