openvidu-browser: Log MediaStream ID instead of whole object
openvidu-browser: Log MediaStream ID instead of whole object

Log the MediaStream ID, which is a string, instead of the mediaStream
object, which showed up as "[object MediaStream]" in the logs.

OpenVidu/openvidu,OpenVidu/openvidu,OpenVidu/openvidu,OpenVidu/openvidu,OpenVidu/openvidu,OpenVidu/openvidu