We should be proactive in ensuring that the environment is clean when
running a task. We already ensure that we have a clean renderer and
other parts of the output chain, but we were not setting a clean user.
This change adds a call to setup the cron user before each task is
actually executed.
* CLI adhoc_task.php: new option --taskslimit
* CLI adhoc_task.php: --execute option is implied when other options are given
* core\task\manager::get_next_adhoc_task(): new param $number
for limiting number of tasks to run
* CLI adhoc_task.php: new option --id
* cron::run_adhoc_task($taskid) for running tasks by id
* core\task\manager::get_adhoc_task($taskid) for retreival/locking
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.
