Bug 1487278: When a transceiver is stopped/disassociated by a remote description, clear its transport id too. r=mjf

Differential Revision: https://phabricator.services.mozilla.com/D11778

--HG--
extra : moz-landing-system : lando

media/webrtc/signaling/src/jsep/JsepSessionImpl.cpp

@@ -1611,6 +1611,7 @@ JsepSessionImpl::UpdateTransceiversFromRemoteDescription(const Sdp& remote)
         mUsedMids.insert(transceiver->GetMid());
       }
     } else {
+      transceiver->mTransport.Close();
       transceiver->Disassociate();
       // This cannot be rolled back.
       transceiver->Stop();