Remove temporary SetConfig method from NetworkSimulatioInterface and makes minor cleanup. Bug: webrtc:9630 Change-Id: If472da7c21ffc9c83fe8b80e6665c3d5fb94382b Reviewed-on: https://webrtc-review.googlesource.com/95644 Reviewed-by: Patrik Höglund <phoglund@webrtc.org> Commit-Queue: Artem Titov <titovartem@webrtc.org> Cr-Commit-Position: refs/heads/master@{#24400}