Revert "Turn on IPv6 for WebRTC as default as required before ramping the experiment to 30%."
Revert "Turn on IPv6 for WebRTC as default as required before ramping the experiment to 30%."

This reverts commit bbbdeed2bff31777ca7d298d17336fe94626f5b3.

TBR=juberti@webrtc.org
BUG=

Review URL: https://webrtc-codereview.appspot.com/41109004

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#8585}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: fc2f146af22dc5ba8d53d6e9ff1b7a93fa412d24

sippet/talk,dcpang/fatline-libjingle,sippet/talk,sippet/talk,dcpang/fatline-libjingle,sippet/talk,dcpang/fatline-libjingle,dcpang/fatline-libjingle,dcpang/fatline-libjingle,sippet/talk