fix lock order

the producer should have the T_FINAL lock before making the node
available by releasing the tree lock

src/vdp_pesi.c

@@ -2469,9 +2469,10 @@ vped_deliver(struct req *req, struct boc *boc, int wantbody)
 
 		if (parent->state != ST_PRIVATE)
 			AZ(pthread_cond_signal(&tree->cond));
-		Lck_Unlock(&tree->tree_lock);
 
 		AZ(pthread_mutex_lock(&node->final.fi_mtx));
+		Lck_Unlock(&tree->tree_lock);
+
 		if (node->final.fi_state < FI_GO)
 			AZ(pthread_cond_wait(&node->final.fi_cond,
 					     &node->final.fi_mtx));