Data channel test currently reliant on internal signaller id

[DamonOehlman]

see: https://github.com/rtc-io/rtc-quickconnect-test/blob/master/test/datachannel.js#L39

This does not work in a world of ids communicated from the server not matching with the self-assigned client id. Needs to be fixed.

[DamonOehlman]

Done significant rework to make this the case and published 1.2.0 - currently being reviewed to see if it's worked with an implementation that does announce with an id different to what is communicated to the server.