Meet: Fix replaceTrack() bug

Summary:
Fixes a bug in Chrome where you would start hearing yourself after audio device change
https://github.com/OpenVidu/openvidu/issues/449

Test Plan: ./phpunit

Reviewers: #hkccp_developers, vanmeeuwen

Reviewed By: #hkccp_developers, vanmeeuwen

Subscribers: #hkccp_developers

Differential Revision: https://git.kolab.org/D2227