webrtc wpt: add missing pc.close during cleanup

running the html.js/codemod-peerconnection-addcleanup from the tools directory showed some places where a pc.close was missing

BUG=836871

Change-Id: I135db200a4269eccfafc43217b66584603101434
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1610767
Commit-Queue: Philipp Hancke <philipp.hancke@googlemail.com>
Reviewed-by: Henrik Boström <hbos@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661283}
5 files changed