Current implementation of lxc driver creates vethN named
interface(s) in the host and passes as it is to a container.
The reason why it doesn't use ethN is due to the limitation
that one namespace cannot have multiple iterfaces that have
an identical name so that we give up creating ethN named
interface in the host for the container.

However, we should be able to allow the container to have
ethN by changing the name after clone(CLONE_NEWNET).

* src/lxc/lxc_container.c src/lxc/veth.c src/lxc/veth.h: do the clone
  and then renames interfaces eth0 ... ethN to keep the interface names
  familiar in the domain