Add "x"s in the end of a stripped IPv6 address string.

This makes it clearer that the IP address has been stripped.

BUG=chromium:254329

Review URL: https://codereview.webrtc.org/1516163003

Cr-Original-Commit-Position: refs/heads/master@{#11005}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: ac921d7365e83b1e271e05a2654ef705de5c60b7
3 files changed