Error messages when options are duplicated

[Chihiro Ito]

I would like to fix an error message when the same option is specified
multiple times for -XX:StartFlightRecording.

Currently the error message is "Duplicates in diagnostic command arguments".

My client and I were unable to quickly figure out what was wrong with
this message, so we searched for this message on GitHub and noticed
that the same option was specified multiple times for
-XX:StartFlightRecording.

How about the following to make this more noticeable?

filename is duplicated in starting FlightRecording
disk and filename are duplicated in starting FlightRecording
disk, filename and name are duplicated in starting FlightRecording

I can PR it right away, as it is already implemented and working good.

Best regards,
Chihiro