RFR: 8242328: Update mentions of ThreadMBean to ThreadMXBean

[Igor Ignatyev]

LGTM

-- Igor

> On Jun 11, 2020, at 2:09 PM, Leonid Mesnik <leonid.mesnik at oracle.com> wrote:
> 
> Hi
> 
> Could you review following fix which change leftovers of ThreadMBean to ThreadMXBean. In the most cases the comments were updated only.
> 
> webrev: http://cr.openjdk.java.net/~lmesnik/8242328/webrev.00/
> 
> bug: https://bugs.openjdk.java.net/browse/JDK-8242328
> 
> Leonid
>