groonga-httpd: fix a bug "off" is used as path name in groonga_query_log_path
groonga-httpd: fix a bug "off" is used as path name in groonga_query_log_path

[groonga-dev,02113]

Reported by Ryoji Yamamoto. Thanks!!!

cosmo0920/groonga,redfigure/groonga,naoa/groonga,myokoym/groonga,hiroyuki-sato/groonga,myokoym/groonga,cosmo0920/groonga,naoa/groonga,cosmo0920/groonga,redfigure/groonga,groonga/groonga,redfigure/groonga,myokoym/groonga,myokoym/groonga,kenhys/groonga,hiroyuki-sato/groonga,naoa/groonga,kenhys/groonga,kenhys/groonga,hiroyuki-sato/groonga,cosmo0920/groonga,redfigure/groonga,redfigure/groonga,myokoym/groonga,hiroyuki-sato/groonga,komainu8/groonga,naoa/groonga,naoa/groonga,redfigure/groonga,naoa/groonga,komainu8/groonga,kenhys/groonga,groonga/groonga,hiroyuki-sato/groonga,hiroyuki-sato/groonga,myokoym/groonga,myokoym/groonga,redfigure/groonga,hiroyuki-sato/groonga,kenhys/groonga,groonga/groonga,komainu8/groonga,kenhys/groonga,groonga/groonga,groonga/groonga,naoa/groonga,komainu8/groonga,myokoym/groonga,kenhys/groonga,redfigure/groonga,groonga/groonga,komainu8/groonga,hiroyuki-sato/groonga,groonga/groonga,komainu8/groonga,cosmo0920/groonga,naoa/groonga,komainu8/groonga,groonga/groonga,komainu8/groonga,cosmo0920/groonga,cosmo0920/groonga,cosmo0920/groonga,kenhys/groonga