Major Description
The description is:
The slave is killed before the update reaches the scheduler. When the slave comes back up it resends the unacknowledged update"
But in the test code, the StatusUpdateMessage is dropped, so there is no checkpointing for status update involved at all. It's the executor resends the unacknowledged status updates when reconnecting, rather than the slave "resends the unacknowledged update". This means this test is the same with SlaveRecoveryTest.ReconnectExecutor, which doesn't make sense.
To fix it, we should drop the StatusUpdateAcknowledgementMessage instead of the StatusUpdateMessage.