Don't log warning for unexpected STUN binding responses.
Don't log warning for unexpected STUN binding responses.

It was too spammy in the log because we have many code paths that check for responses when it's not a problem that it's not an expected response.

R=glaznev@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/47199004

Cr-Original-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#9212}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 3e95d3ef39c0e5e13d697dab9a8abea0e72feb4e

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