MAGN-5103 Select Face goes into infinite loop when ModelCurve in graph, Run auto on

Partial fix for MAGN-5103

http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-5103

Requires merge:
- [x] Revit2015

PTAL:
@Steell 
@ikeough, ```OnEvaluationCompleted``` is called on a background thread (in both the old ```DynamoRunner``` and the new ```DynamoScheduler```). For all we know there is nothing guarding the UI thread from modifying ```HomeSpace.Nodes``` list when this iterator runs and crash on invalid enumerator. For this to work 100% of the time, it needs to go on UI thread (at least in standalone mode). What say?