Requeueing the tasks of a specific worker is now done in the
`TaskStateMachine`, such that it can be called from other services as
well in future commits.
This also makes the `LogStorage` service a dependency of the
`TaskStateMachine`, as it needs to write "this task was requeued" kind
of messages to the task logs.
In the future different services will write to the task log, and thus
it makes sense to move the responsibility of prepending the timestamps
to the log storage service.
