fix event name in alert history on status change
fix event name in alert history on status change

mrkeng/alerta,skob/alerta,guardian/alerta,mrkeng/alerta,mrkeng/alerta,guardian/alerta,0312birdzhang/alerta,guardian/alerta,skob/alerta,skob/alerta,0312birdzhang/alerta,skob/alerta,0312birdzhang/alerta,guardian/alerta,mrkeng/alerta