Test fails intermittently (high rate) on MacOSX 10.9.5 / Mac Book Pro 2.7GHz Intel Core I7 16Gb 1600 MHz DDR3
Switch to System.nanoTime()

git-svn-id: https://svn.apache.org/repos/asf/jmeter/trunk@1628263 13f79535-47bb-0310-9956-ffa450edef68