RFR 8133666: OperatingSystemMXBean reports abnormally high machine CPU consumption on Linux

[david buck]

Hi!

Please review my fix for this JMX issue.

bug: https://bugs.openjdk.java.net/browse/JDK-8133666
webrev: http://cr.openjdk.java.net/~dbuck/8133666/

Once approved, I will push this fix into:

http://hg.openjdk.java.net/jdk9/hs-rt

Cheers,
-Buck