Disable CanSwitchToUseAllSsrcs on DrMemory.

Test times out.

R=mflodman@webrtc.org
BUG=3159

Review URL: https://webrtc-codereview.appspot.com/13799004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6566 4adac7df-926f-26a2-2b94-8c16560cd09d