Adapt MailboxChangesMethodContract for stability against distributed environment

Objective

Because changes in distributed environment do not happen instantaneously, we need to adapt the contract so that the tests behave in a more reliable way.

How

Before, we were storing a state manually as a reference point, then the change(s) that we interested in would be conducted after that. This will not work in distributed environment, since the reference state might be stored even before the provisioning process complete and leads to unpredictable result.

• We will wait for a new state to be recorded successfully each time there is a change happen
• Fetch them sequentially until all the preparation steps are completed
• Mark the latest stage
• Conduct the change that we are interested in
• fetch the result with the latest state as reference point.

DoD

Integration tests for MailboxChangesMethod should run reliably in distributed environment.