In multiqueue, all NetClientState that belongs to the same netdev or nic has the
same id. So this patches introduces an helper qemu_find_net_clients_except()
which finds all NetClientState with the same id. This will be used by multiqueue
networking.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>