Fix polling on restart for running tasks.

Fixes a bug in restarting for running tasks whereby the wrong status file would be polled.

Sequence to replicate the bug is as follows:

 * Task runs and fails
 * Task is reset to waiting
 * Suite shutdown once task running but before finishes
 * Task succeeds
 * Suite restarted
 * Task.1.1.status incorrectly polled, setting task to failed state