appveyor: disable grntest
appveyor: disable grntest

Because grntest doesn't work on Windows. We can't use pipe to
communicate child process on Windows. We should use TCP socket instead.

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