Handle the return value of write to suppress a warning
Handle the return value of write to suppress a warning

This change suppresses the following warning (gcc):
  groonga.c: In function ‘send_ready_notify’:
  groonga.c:806:5: warning: ignoring return value of ‘write’, declared with attribute warn_unused_result [-Wunused-result]
       write(ready_notify_pipe[PIPE_WRITE],
       ^

kenhys/groonga,komainu8/groonga,kenhys/groonga,groonga/groonga,kenhys/groonga,cosmo0920/groonga,cosmo0920/groonga,cosmo0920/groonga,kenhys/groonga,komainu8/groonga,kenhys/groonga,komainu8/groonga,komainu8/groonga,naoa/groonga,groonga/groonga,cosmo0920/groonga,cosmo0920/groonga,naoa/groonga,naoa/groonga,cosmo0920/groonga,komainu8/groonga,komainu8/groonga,groonga/groonga,groonga/groonga,naoa/groonga,naoa/groonga,naoa/groonga,komainu8/groonga,komainu8/groonga,naoa/groonga,groonga/groonga,cosmo0920/groonga,cosmo0920/groonga,kenhys/groonga,groonga/groonga,groonga/groonga,kenhys/groonga,kenhys/groonga,groonga/groonga,naoa/groonga