zebra: fix output of IPv6 ND RA options

The following options could be configured for an interface, but were
never visible in the config text:

ipv6 nd adv-interval-option
ipv6 nd home-agent-preference
ipv6 nd home-agent-lifetime
ipv6 nd home-agent-config-flag
diff --git a/zebra/rtadv.c b/zebra/rtadv.c
index e094135..bc1abca 100644
--- a/zebra/rtadv.c
+++ b/zebra/rtadv.c
@@ -1511,10 +1511,24 @@
       vty_out (vty, " ipv6 nd ra-interval %d%s", interval / 1000,
 	     VTY_NEWLINE);
 
+  if (zif->rtadv.AdvIntervalOption)
+    vty_out (vty, " ipv6 nd adv-interval-option%s", VTY_NEWLINE);
+
   if (zif->rtadv.AdvDefaultLifetime != RTADV_ADV_DEFAULT_LIFETIME)
     vty_out (vty, " ipv6 nd ra-lifetime %d%s", zif->rtadv.AdvDefaultLifetime,
 	     VTY_NEWLINE);
 
+  if (zif->rtadv.HomeAgentPreference)
+    vty_out (vty, " ipv6 nd home-agent-preference %u%s",
+	     zif->rtadv.HomeAgentPreference, VTY_NEWLINE);
+
+  if (zif->rtadv.HomeAgentLifetime)
+    vty_out (vty, " ipv6 nd home-agent-lifetime %u%s",
+	     zif->rtadv.HomeAgentLifetime, VTY_NEWLINE);
+
+  if (zif->rtadv.AdvHomeAgentFlag)
+    vty_out (vty, " ipv6 nd home-agent-config-flag%s", VTY_NEWLINE);
+
   if (zif->rtadv.AdvReachableTime)
     vty_out (vty, " ipv6 nd reachable-time %d%s", zif->rtadv.AdvReachableTime,
 	     VTY_NEWLINE);