RFR: 8078144 many nightly tests failed due to NoSuchMethodError: sun.management.ManagementFactoryHelper.getDiagnosticMXBean

[Shanliang Jiang]

Hi,

Please review this test fix:
webrev: http://cr.openjdk.java.net/~sjiang/JDK-8078144/00/
bug: https://bugs.openjdk.java.net/browse/JDK-8078144

The method sun.management.ManagementFactoryHelper.getDiagnosticMXBean 
was removed because HotSpotDiagnosticMXBean is not in java.management 
module but in jdk.management module, to get the HotSpotDiagnosticMXBean 
we should call:
    ManagementFactory.getPlatformMXBean(HotSpotDiagnosticMXBean.class)

I passed all failed tests with the fix.

Thanks,
Shanliang