Http server: ifconfig to return MAC address

To return the interface MAC address, the libtools interface definition
was added a phys_addr parameter, the interface is passed now for the
set_intrface info method, this will allow settting additional parameters
that are not in the ifnet structure.

An equivelent parameter was added to the API and is now return with a
call to:
http://localhost:8000/network/ifconfig/

Signed-off-by: Amnon Heiman <amnon@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>