net: bootp: Fall back to BOOTP from DHCP when unit testing

net: bootp: Fall back to BOOTP from DHCP when unit testing

If we sent a DHCP packet and get a BOOTP response from the server, we
shouldn't try to send a DHCPREQUEST packet, since it won't be DHCPACKed.
Transition straight to BIND. This is only enabled for UNIT_TEST to avoid
bloat, since I suspect the number of BOOTP servers in the wild is
vanishingly small.

Signed-off-by: Sean Anderson <seanga2@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>