When fetching the list of tasks to run, we were using the _process_
start time as a base. The various task fetchers (adhoc and scheduled)
only fetch tasks which were due to run _before_ this time.
With the new keepalive setting, we need to pass both the process start
time, and the run start time. We need to use the process start time to
determine whether MUC caches have been cleared since the process
started. but the run start time to fetch recent runs.
Andrew Nicols