Include the modified nodes into the reachable list

1. The modified nodes are always going to be executed. They should
always be added to the reachable guid list
2. Modified the testcases to reflect this
Merge branch 'master' of https://github.com/DynamoDS/Dynamo into defectfix
Revert minor change
Merge pull request #3371 from junmendoza/defectfix

Include the modified nodes into the list of reachable node list