RFR : JDK-8024352 - MBeanOperationInfo accepts any int value as "impact"

[Ujwal Vangapally]

Kindly review the fix for bug below.

https://bugs.openjdk.java.net/browse/JDK-8024352
webrev : 
http://cr.openjdk.java.net/~uvangapally/webrev/2017/8024352/webrev.00/

Thanks,

Ujwal.