Bug970187, Bug970187, CDMA-3way calls

It correspondence of reviews.
https://github.com/mozilla-b2g/gaia/pull/19976

https://bugzilla.mozilla.org/show_bug.cgi?id=970187
As Anthony mentioned on the bug you can remove this and use sinon instead. For example in the test above you could do:

```javascript
test('should toggle no-add-call in cdma network', function() {
  MockNavigatorMozMobileConnections[1].voice = {
    type: 'evdoa'
  };
  MockNavigatorMozTelephony.calls = [mockCall, '123456789'];
  this.sinon.spy(MockCallScreen, 'hidePlaceNewCallButton');

  MockNavigatorMozTelephony.mTriggerCallsChanged();
  sinon.assert.calledOnce(MockCallScreen.hidePlaceNewCallButton);
});
```