When calling "getSettings" on a MediaStreamTrack, return a correct value for "echoCancellation" - true if echo cancellation is turned on, false if echo cancellation is turned off.

Spec reference: https://w3c.github.io/mediacapture-main/getusermedia.html#dom-mediatracksettings-echocancellation

This has been requested during intent-to-ship discussion for getSettings.