the linkage between physnet and the port status in vm.

The linkage between physnet and the port used in vm.
When the NIC which configed by physnet is down the packet can't be send out of the host NIC.But the port statue of vm is still up when we use in ovs.
The VM don't know that the packet can not send out of the host now.This will make mistake.
So we need a linkage between them.Just like sriov, when the pf is down the vf should be down.
But in some case, even the physnet is down ,the traffic between vm in the same host won't be affected.
So we need the linkage between the physnet and the vm port and we also need a configure option to use it or not.