WebStyle: fix gotoadmin CLI parmeters parsing

* Fixed parsing of gotoadmin CLI '--json-parameters' and
  '--parameter' options.
  (closes #1427)

Co-authored-by: Samuele Kaplun <samuele.kaplun@cern.ch>
Reviewed-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>