[SimNodes] Add config/flag specifying whether commissioning should occur pre-test or not.

[trombadore-google]

Problem

For simulated node YAML tests, commissioning must complete before testing starts. Some controller certification tests will need to test their ability to walk through node commissioning flow. Therefore, weather commissioning should occur pre-test or not should be up to the script writer.

Proposed Solution

Add a config in YAML or runtime flag to specify weather commissioning should occur prior to a simulated node test's start or not.