Fix a bug in SocketAddress where "a.b.c.d:1" and "b.b.c.d:1" are incorrectly considered equal.

BUG=3558
R=mallinath@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/18749004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6639 4adac7df-926f-26a2-2b94-8c16560cd09d