The ThreadCpuTime.java j.l.m unit test uses a value DELTA as the minimum difference
between successive calls to getThread{Cpu|User}Time(). This is dubious, as the
comment "careful about this value" says. Presumably the actual delta between
successive calls varies from platform to platform. It may be possible to eliminate
the test entirely.

The code for test/com/sun/management/ThreadMXBean/ThreadCpuTimeArray.java was borrowed
from ThreadCpuTime.java, thus uses DELTA in the same way. It should be fixed also.