* support proper addworker rollback

* fix followup

* drop sync keyword

* fix CI test failures from prior commits

- testJobSubmitInitalizationFails: actor now stops on submit-time
  init failure, so assert termination instead of expecting a follow-up
  GetJobDetailsResponse.

- testWorkerAcceptedToStartedMsRecordedOnWorkerStatus: SpectatorRegistryFactory.setRegistry
  is a one-shot CAS, so when JobScaleUpDownTests installs a registry first
  this test was reading a different DefaultRegistry instance than the one
  actually wired up. Read the installed registry via getRegistry() instead.