ospf6d: improve ordered shutdown

Improve the _disable/_enable infrastructure so it gets into
a more usable shape and make 'no router ospf6' actually work.

Signed-off-by: Christian Franke <chris@opensourcerouting.org>
Signed-off-by: David Lamparter <equinox@opensourcerouting.org>
diff --git a/ospf6d/ospf6_zebra.c b/ospf6d/ospf6_zebra.c
index f09e9d2..50ecc17 100644
--- a/ospf6d/ospf6_zebra.c
+++ b/ospf6d/ospf6_zebra.c
@@ -117,7 +117,9 @@
 		ifp->name, ifp->ifindex, ifp->mtu6);
 
 #if 0
-  /* Why is this commented out? */
+  /* XXX: ospf6_interface_if_del is not the right way to handle this,
+   * because among other thinkable issues, it will also clear all
+   * settings as they are contained in the struct ospf6_interface. */
   ospf6_interface_if_del (ifp);
 #endif /*0*/