DHCP client: Fix setting of 'clientHwAddr'

'clientHwAddr' is the raw MAC address, so the control function is
ETH_CTRL_GET_MAC, not NET_GET_HWADDR.  This was causing the DHCP client
to send out packets with a bogus MAC address.

Reported-by: Arjan van Vught <arjan.van.vught@gmail.com>
DHCP client: increase 'recvTimeout'

Two seconds is too short.  Some DHCP servers take longer to respond,
usually because they send out ARP requests for the address about to be
assigned.

Reported-by: Arjan van Vught <arjan.van.vught@gmail.com>