Disable flaky test (WebRtcVideoMediaChannelTest.GetStats) on DrMemory Full.

BUG=3482
R=kjellander@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/20649004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6440 4adac7df-926f-26a2-2b94-8c16560cd09d