Improve scan load updation on scan timeouts

We use "avgLoad" (represents scan load on an instance, decided by scan response time) as one of the deciding factors for selection of instance for processing scan request.

Issue: The scan avgLoad is not updated if scan returns an error. This includes case where scan timeouts are happening which lead to wrong value of scan load and the instance being given more load even when it can be timing out due to high load.

Ask is to have the avgLoad account for scan load being generated when there are timeouts occurring.