Set broadcast when sending DHCPREQUEST and DHCPDISCOVER

Set broadcast when sending DHCPREQUEST and DHCPDISCOVER

We need to do this, since our devices are probably not configured yet and
there may be more than one device we're trying to do DHCP on on the same
network. Otherwise, things might be dropped.

Patch is originally from here:
https://bugs.launchpad.net/ubuntu/+source/klibc/+bug/1327412/comments/5
... but the reporter "patpat" has not provided contact information, and
this is independently verifiable by looking at RFC 2131, section 4.1,
page 24.

Gbp-Pq: Name broadcast_dhcp_send.patch