Remove deprecated IsUnresolved() method from SocketAddress API.

This patch removes IsUnresolved() method and update the clients to use
IsUnresolvedIP() instead.

BUG=None
R=perkj@webrtc.org
TBR=glaznev@webrtc.org

Review URL: https://codereview.webrtc.org/1414793006

Cr-Original-Commit-Position: refs/heads/master@{#10487}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 20a34619080005c3b0e49d85b307113ea2b180c3
8 files changed