Removes unnecessary creation/removal of intermediate VideoSendStreams due to only being partially configured before creation. BUG=webrtc:5296, webrtc:5410 R=deadbeef@webrtc.org, pthatcher@webrtc.org Review URL: https://codereview.webrtc.org/1561073006 . Cr-Commit-Position: refs/heads/master@{#11399}