ocfs2/cluster: Check slots for unconfigured live nodes

o2hb currently checks slots for configured nodes only. This patch makes
it check the slots for the live nodes too to take care of a race in which
a node is removed from the configuration but not from the live map.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
diff --git a/fs/ocfs2/cluster/tcp.c b/fs/ocfs2/cluster/tcp.c
index cbe2f05..9aa426e 100644
--- a/fs/ocfs2/cluster/tcp.c
+++ b/fs/ocfs2/cluster/tcp.c
@@ -1696,6 +1696,9 @@
 {
 	o2quo_hb_down(node_num);
 
+	if (!node)
+		return;
+
 	if (node_num != o2nm_this_node())
 		o2net_disconnect_node(node);
 
@@ -1709,6 +1712,8 @@
 
 	o2quo_hb_up(node_num);
 
+	BUG_ON(!node);
+
 	/* ensure an immediate connect attempt */
 	nn->nn_last_connect_attempt = jiffies -
 		(msecs_to_jiffies(o2net_reconnect_delay()) + 1);