Preparing simple worker tasks is super fast, because it just switches the state to null.
But the processing of just prepared tasks required the second worker run and also second cron run.
This change optimize the behavior and in case there is still time left it immediately starts processing the tasks.
[MAILPOET-4684]
Sometimes errors overlap each other so that the 'Last Seen error' we log
does not provide sufficient information on the cause of a problem.
E.g. one worker might cause an SQL issue, which closes the EntityManager and a
subsequent worker might overwrite this error with the information that the
EntityManager is closed.
With this commit, both those issues will be logged as an error.
[MAILPOET-4699]
