WebRTC can not be disabled globally on V2 (since it is superior option to Flash).
There is still a way to disable it, however it is done for specific embedding. To do that you would add "forceflash" parameter to your recorder.
This is an example on how to do it:
<ziggeorecorder ziggeo-theme="modern" ziggeo-themecolor="red" ziggeo-forceflash></ziggeorecorder>