Schema changes of Ecmp load balancing configuration.
Schema changes of Ecmp load balancing configuration.

This change enables user to choose fields to do load balance in ecmp nexthops.
These criterias can be specified at interface/VN/global level.

Change-Id: Ibd349bc156deaff77af4b126f953077f8344d339
Partial-bug: 1498765

tcpcloud/contrail-controller,nischalsheth/contrail-controller,sajuptpm/contrail-controller,tcpcloud/contrail-controller,rombie/contrail-controller,nischalsheth/contrail-controller,tcpcloud/contrail-controller,eonpatapon/contrail-controller,nischalsheth/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,codilime/contrail-controller,rombie/contrail-controller,sajuptpm/contrail-controller,codilime/contrail-controller,codilime/contrail-controller,nischalsheth/contrail-controller,sajuptpm/contrail-controller,tcpcloud/contrail-controller,rombie/contrail-controller,codilime/contrail-controller,tcpcloud/contrail-controller,nischalsheth/contrail-controller,rombie/contrail-controller,nischalsheth/contrail-controller,sajuptpm/contrail-controller,eonpatapon/contrail-controller,rombie/contrail-controller,codilime/contrail-controller,nischalsheth/contrail-controller,eonpatapon/contrail-controller,eonpatapon/contrail-controller,sajuptpm/contrail-controller,eonpatapon/contrail-controller,tcpcloud/contrail-controller,rombie/contrail-controller,eonpatapon/contrail-controller,codilime/contrail-controller,sajuptpm/contrail-controller,nischalsheth/contrail-controller