OSPF: DD seqnum should be initialized only for first attempts

After SeqNumberMismatch/BadLSReq, we should continue with the old
seqnum++. The old code tries to do that by n->adj, but it was set
nowhere.

proto/ospf/neighbor.c

@@ -176,8 +176,8 @@ ospf_neigh_chstate(struct ospf_neighbor *n, u8 state)
 
   if (state == NEIGHBOR_EXSTART)
   {
-    /* First time adjacency */
-    if (n->adj == 0)
+    /* First time adjacency attempt */
+    if (old_state < NEIGHBOR_EXSTART)
       n->dds = random_u32();
 
     n->dds++;

proto/ospf/ospf.h

@@ -353,7 +353,6 @@ struct ospf_neighbor
   u32 rid;			/* Router ID */
   ip_addr ip;			/* IP of it's interface */
   u8 priority;			/* Priority */
-  u8 adj;			/* built adjacency? */
   u32 options;			/* Options received */
 
   /* Entries dr and bdr store IP addresses in OSPFv2 and router IDs in