BHV-15359: List item shows incorrect result when it has an checkbox item and bind with model's selected property

### Issue:
Problems when you combine binding a model property to a checkbox, with using the selectionProperty attribute
### Fix:
when a control is assigned a model in generatePage(), add a check to synchronize the model property with the list's selections

Enyo-DCO-1.1-Signed-off-by: Krishna Rangarajan <krishna.rangarajan@lge.com>
Could we return a boolean from this method that represents whether or not this current control is selected in the list, and use this in the next line, so we don't have to run `list.isSelected` multiple times per control?