Exclude SctpDataMediaChannelTest on Win DrMemory for third_party/usrsctp issues.

TBR=wu@webrtc.org
BUG=3492

Review URL: https://webrtc-codereview.appspot.com/14719004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6485 4adac7df-926f-26a2-2b94-8c16560cd09d