Disable PhysicalSocketTest.TestUdpReadyToSendIPv4 for TSAN2

BUG=webrtc:3498
R=henrik.lundin@webrtc.org
TBR=tommi

Review URL: https://webrtc-codereview.appspot.com/21689005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6528 4adac7df-926f-26a2-2b94-8c16560cd09d