Fix to delete fip pool while deleting VN only when there are no references to VMI
Fix to delete fip pool while deleting VN only when there are no references to VMI

hari-sk/contrail-web-core,biswajit-mandal/contrail-web-core,vishnuvv/contrail-web-core,hari-sk/contrail-web-core,varunarya10/contrail-web-core,hari-sk/contrail-web-core,vishnuvv/contrail-web-core,nagakiran/contrail-web-core,vishnuvv/contrail-web-core,varunarya10/contrail-web-core,varunarya10/contrail-web-core,biswajit-mandal/contrail-web-core,biswajit-mandal/contrail-web-core,nagakiran/contrail-web-core,manojgn/contrail-web-core,nagakiran/contrail-web-core,manojgn/contrail-web-core