Disable CallPerfTest.CaptureNtpTimeWithNetworkDelay due to being flaky.

TBR=wu@webrtc.org
BUG=3374

Review URL: https://webrtc-codereview.appspot.com/14579005

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6201 4adac7df-926f-26a2-2b94-8c16560cd09d