RFR:8207048: jhsdb debugd cannot specify a port number

[KUBOTA Yuji]

Hi all,

I filed bugzilla for small fix to improvement of `jhsdb debugd` to set
a port of UnicastRemoteObject aka
sun.jvm.hotspot.debugger.remote.RemoteDebuggerServer by
`sun.jvm.hotspot.rmi.debugger.port`.

Issue: https://bugs.openjdk.java.net/browse/JDK-8207048
Webrev: http://cr.openjdk.java.net/~ykubota/8207048/webrev.00/

We can set an RMI registry port of debugd server by
`sun.jvm.hotspot.rmi.port`, but can not set a port of RemoteObject. So
RemoteObject always uses an anonymous port. For security, we should
not open ports widely to use debugd, so I want to fix.

Could you review it?

Thanks,
Yuji