ospfd: Fix various route_unlock discrepencies

* ospf_ase.c: (ospf_ase_calculate_route) Fix compiler warning about eval
  needing brackets.
  (various) add defensive asserts.
* ospf_lsdb.c: (ospf_lsdb_add) add missing node unlock if same lsa already
  was indexed.
  (ospf_lsdb_delete) check it's actually the same as specified lsa before
  deleting
  (ospf_lsdb_lookup_by_id_next) fix another corner case - no result =>
  don't go on.
diff --git a/ospfd/ospf_lsdb.c b/ospfd/ospf_lsdb.c
index c906f05..ea9a352 100644
--- a/ospfd/ospf_lsdb.c
+++ b/ospfd/ospf_lsdb.c
@@ -120,7 +120,10 @@
   
   /* nothing to do? */
   if (rn->info && rn->info == lsa)
-    return;
+    {
+      route_unlock_node (rn);
+      return;
+    }
   
   /* purge old entry? */
   if (rn->info)
@@ -162,12 +165,13 @@
       return;
     }
   
+  assert (lsa->data->type < OSPF_MAX_LSA);
   table = lsdb->type[lsa->data->type].db;
   lsdb_prefix_set (&lp, lsa);
-  rn = route_node_lookup (table, (struct prefix *) &lp);
-  if (rn && (rn->info == lsa))
+  if ((rn = route_node_lookup (table, (struct prefix *) &lp)))
     {
-      ospf_lsdb_delete_entry (lsdb, rn);
+      if (rn->info == lsa)
+        ospf_lsdb_delete_entry (lsdb, rn);
       route_unlock_node (rn); /* route_node_lookup */
     }
 }
@@ -274,7 +278,8 @@
       rn = route_top (table);
   else
     {
-      rn = route_node_get (table, (struct prefix *) &lp);
+      if ((rn = route_node_lookup (table, (struct prefix *) &lp)) == NULL)
+        return NULL;
       rn = route_next (rn);
     }