Bug 1069169 - [callscreen] unittest call_sccreen_test.js incorrect using assert.include for testing existing object

```javascript
746: assert.include(bannerClass, 'visible');
```
assert.include - test inclusion of an object in another. Works for strings and Arrays, for other do nothing!!

later similar testing this property 
```javascript
        test('should hide the banner', function() {
          assert.isFalse(bannerClass.contains('visible'));
        });
```