maxVideoBW setting does not work for VP9

[vpoddubchak]

Description When I try to limit publisher bandwidth by updateConfiguration({maxVideoBW:200}) it does nothing.

Steps to reproduce the issue:

1. Run latest docker licode:develop
2. Change ./licode/rtp_media_config.js to use vp9 by default: default: { rtpMappings: { vp9, opus }, extMappings },
3. Add one line stream.updateConfiguration({maxVideoBW:200}); to ./licode/extras/basic_example/public/script.js to limit bitrate:

      const stream = streamEvent.stream;
      const div = document.createElement('div');
      div.setAttribute('style', 'width: 320px; height: 240px;float:left;');
      div.setAttribute('id', `test${stream.getID()}`);

      document.getElementById('videoContainer').appendChild(div);
      stream.updateConfiguration({maxVideoBW:200});
      stream.show(`test${stream.getID()}`);
    });

4. Commit changes and restart container
5. Open first page: http://localhost:3001/
6. See sending statistic in chrome://webrtc-internals : bitrate is ~ 280kbps
7. Open second page: http://localhost:3001/?onlySubscribe=true
8. See that sending bitrate does not change: still ~ 280 kbps

Describe the results you expected: I expect to drop publish bitrate to ~200 kbps

Additional information you deem important (e.g. issue happens only occasionally): It does not reproduce if use default vp8 codec.