Fix dhcpd/dhcrelay in v6 mode operation on OpenBSD

The linked diff has been in our tree for quite awhile. It fixes v6 mode operation of dhcpd/dhcrelay on OpenBSD. sin6_scope_id needs to be set not just for dhclient but also for dhcpd/dhcrelay.

http://cvsweb.openbsd.org/cgi-bin/cvsweb/~checkout~/ports/net/isc-dhcp/patches/patch-common_socket_c?rev=1.7&content-type=text/plain&hideattic=1