Need subnet state in order to configure the router.

[zzxgzgz]

In the current ACA implementation, when create/update a router, ACA code will look into the GS that the router state is in, for subnet states. Need to investigate if it is possible to leverage the subnet info already stored in the ACA itself.

Related code:
GSV1:
https://github.com/futurewei-cloud/alcor-control-agent/blob/master/src/ovs/aca_ovs_l3_programmer.cpp#L161

GSV2:
https://github.com/futurewei-cloud/alcor-control-agent/blob/master/src/ovs/aca_ovs_l3_programmer.cpp#L566