Treat delete followed by add in route as "AddEvent"
Treat delete followed by add in route as "AddEvent"

Change-Id: Ifbfe7108013f8b6ea57f55f4a8b614d198773858
Closes-Bug: #1551577

tcpcloud/contrail-controller,tcpcloud/contrail-controller,tcpcloud/contrail-controller,tcpcloud/contrail-controller,tcpcloud/contrail-controller,tcpcloud/contrail-controller