Reason for the error is that --defaults-group-suffix is passed twice
to the command line client, and option parser is not prepared for this.

Double occurence of comes from 2 invocations of parse_arguments(), which
appends unparsed arguments each time it is called.

Fixed by treating --defaults-group-suffix like other "--defaults-"
(--defaults-file/--defaults-extra-file). it will be parsed, and thus
passed only once to the command line client.