Retry Taskmaster
The retry taskmaster will listen on the task bus for failed tasks and when
it receives a failed task will apply any retry rules for that task type.
The retry taskmaster is capable of keeping in-memory state of the particular
task current retry count so that it can apply the retry rule correctly.
If the retry taskmaster is restarted then the in-memory task retry state
is forgotten.
Once a task is successful, the retry taskmaster will log the number
of failed attempts before success and then clear the task retry state
for that task.