Orator cancels TTS on init

UIO+ ran into an issue where dynamically loaded iframes were causing the self voicing to be stopped ( https://issues.gpii.net/browse/GPII-3977 ). It appears the reason is because the iframe loads a new instance of the Orator because each iframe is passed the content scripts. When the Orator is initialized the following model listener is triggered.

        modelListeners: {
            "enabled": {
                listener: "{tts}.cancel",
                namespace: "orator.clearSpeech"
            }
        },

The result is that the TTS is cancelled every time an iframe is loaded.