sv/eth0: make sure eth0 interface is up

this could also be done as

    ip link set dev eth0 up

not sure which is more standard.
`ip` belongs to [`iproute2`](http://www.linuxfoundation.org/collaborate/workgroups/networking/iproute2)
`ifconfig` belongs to [`net-tools`](http://net-tools.sourceforge.net/)