net: Read veth devices

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
net: Assign constant instead of variable reference

This produce less asm code.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
net: Improve net device type matching procedure

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>