A reset of Bwe and rates on network route change triggers switching of the RemoteBitrateEstimator from DelayBasedBwe to RemoteBitrateEstimatorAbsSendTime. This is unexpected, fix this. BUG= R=stefan@webrtc.org Review URL: https://codereview.webrtc.org/2193043002 . Cr-Commit-Position: refs/heads/master@{#13594}