dhcpd supports netcfg

Created by: batonius

Update dhcpd to change network configuration via netcfg.

Notes:

• If the IP got via DHCP differs from the IP in the configuration file, the current implementation of lookup_host stops working since it used the IP from the file and smoltcp ignores responses as unknown. Specifically, the browser stops working since it can't resolve the host, dnsd works fine.