[l3vpn_ecmp] Bug in loadbalancing group not updated after vlxan tunnel deletion

Extra routes were configures behind 2 nexthops behind 2 DPNs. The loadbalancing group was correctly programmed with buckets pointing to the local next hop and the tunnle in each DPN. The vxlan tunnel between the DPNs was deleted. The expected behavior is the the buckets in the loadbalancing group have to be updated and the group should contain only bucket pointing to the local next hop in each DPN. But it was observed that the loadbalancing continue having buckets pointing to the tunnels.