Flag task processing on task submission.

Task proxies are supposed to spawn once they achieve the 'submitted' state, but the flag for a pass through the main task processing loop (including spawning) was not being set on this state, which meant submitted tasks would not spawn immediately if nothing else was happening. Test: a single cycling task that submits to a non-active queue (e.g. 'at' job submission with atd turned off) should submit out to the runahead limit without requiring any suite nudging. This change achieves that.