Increase the threshold for CallPerfTest.CaptureNtpTimeWithNetworkDelay to avoid flaky. BUG=3374 R=stefan@webrtc.org Review URL: https://webrtc-codereview.appspot.com/19529004 git-svn-id: http://webrtc.googlecode.com/svn/trunk@6267 4adac7df-926f-26a2-2b94-8c16560cd09d