Fix for wrong backend roles on standby after the failover

Fix for wrong backend roles on standby after the failover

Pgpool standby nodes were getting the "require_backend_sync" signal before the
active/master Pgpool had finish the failover. As a results the standby was
getting the wrong backend node statuses. The cause was a simple coding mistake
where failover indication function was passed with the wrong argument.

Problem reported by Bo Peng <pengbo@sraoss.co.jp>