groonga: fix returning wrong result after unfinished /d/load data by POST
groonga: fix returning wrong result after unfinished /d/load data by POST

GitHub: fix #860

groonga/groonga,komainu8/groonga,naoa/groonga,komainu8/groonga,groonga/groonga,naoa/groonga,groonga/groonga,groonga/groonga,naoa/groonga,naoa/groonga,kenhys/groonga,komainu8/groonga,groonga/groonga,komainu8/groonga,groonga/groonga,naoa/groonga,naoa/groonga,kenhys/groonga,komainu8/groonga,naoa/groonga,kenhys/groonga,komainu8/groonga,kenhys/groonga,groonga/groonga,kenhys/groonga,kenhys/groonga,kenhys/groonga,kenhys/groonga,groonga/groonga,naoa/groonga,komainu8/groonga,komainu8/groonga