[l3vpn_ecmp] Bug in loadbalancing group programming for directly connected subnet routes

When an extra route is added(extra route with macaddress), the loadbalancing group programmed for ecmp should contain either buckets pointing to the local nexthop group or the tunnels. But in case of the directly connected subnet routes, the groupIds of the loadbalancing group and the local nexthop group turns out to be same, the latter overriding it.