Bug 1094878 - Call is not on hold anymore after hanging up another call even though the icon says it is

Instead of directly calling ```_connect()``` functions and such, we should stub the ```resume()``` function to do this, like so:
```js
this.sinon.stub(MockNavigatorMozTelephony.calls[0].resume, MockNavigatorMozTelephony.calls[0]._resume);
```