According to openJDK sources (both 6 & 7):
http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/6-b14/sun/management/ThreadImpl.java#ThreadImpl.isThreadCpuTimeEnabled()

method (isThreadCpuTimeEnabled) mustn't called if both of isThreadCpuTimeSupported isCurrentThreadCpuTimeSupported returned false.

This commit makes this test safe on platforms which not supported Thread time feature.