Always send preference if it is configured.

See RT ticket #17353 for more.

RELNOTES

@@ -52,6 +52,11 @@ The system has only been tested on Linux, FreeBSD, and Solaris, and
 may not work on other platforms. Please report any problems and 
 suggested fixes to <dhcp-users@isc.org>.
 
+			Changes since 4.0.0rc1
+
+- The DHCPv6 server would not send the preference option unless the 
+  client requested it, via the ORO. This has been fixed, so the DHCPv6
+  server will always send the preference value if it is configured.
 
 			Changes since 4.0.0b3
 

server/dhcpv6.c

@@ -641,6 +641,7 @@ static const int required_opts[] = {
 	D6O_CLIENTID,
 	D6O_SERVERID,
 	D6O_STATUS_CODE,
+	D6O_PREFERENCE,
 	0
 };
 static const int required_opts_solicit[] = {
@@ -652,6 +653,7 @@ static const int required_opts_solicit[] = {
 	D6O_STATUS_CODE,
 	D6O_VENDOR_OPTS,
 	D6O_RECONF_ACCEPT,
+	D6O_PREFERENCE,
 	0
 };
 static const int required_opts_IA_NA[] = {