Only call attributeChanged() when analysis attribute is created

Loading an attribute resource that includes an analysis view into modelbuilder can cause the resource to be marked as modified, because the current qtAnalysisView code presumes the analysis attribute was modified when first loaded. This MR checks whether or not the analysis attribute was created when the view is created in order to prevent the system from inadvertently marking the resource as modified. (In practice, there seems to be a race condition that only causes the problem for some .smtk files.)