Reenable test case P2PTransportChannelTest.TestIPv6Connections
Reenable test case P2PTransportChannelTest.TestIPv6Connections

BUG=3317
R=pthatcher@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/29229004

Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 1f05c45976f730d5310ab63ca1fdf5ba4310e81e

sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc,sippet/webrtc