What version of pgpool are you using?
Are there other commands you have a problem with? I would suspect that the
restart is causing the postgres server to go away, pgpool decides to
disconnect, and then it has to be manually added back to the cluster.
Unless of course you've got automatic failback setup, but even then I would
expect that command to do weird things when issued through middleware like
pgpool, regardless of what sort of infrastructure you are running on.
QH