ocfs2: Abstract out node number queries.

ocfs2 asks the cluster stack for the local node's node number for two
reasons; to fill the slot map and to print it. While the slot map isn't
necessary for userspace cluster stacks, the printing is very nice for
debugging. Thus we add ocfs2_cluster_this_node() as a generic API to get
this value. It is anticipated that the slot map will not be used under a
userspace cluster stack, so validity checks of the node num only need to
exist in the slot map code. Otherwise, it just gets used and printed as an
opaque value.

[ Fixed up some "int" versus "unsigned int" issues and made osb->node_num
  truly opaque. --Mark ]

Signed-off-by: Joel Becker <joel.becker@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>

fs/ocfs2/ocfs2.h

@@ -218,7 +218,7 @@ struct ocfs2_super
 	unsigned int s_atime_quantum;
 
 	unsigned int max_slots;
-	s16 node_num;
+	unsigned int node_num;
 	int slot_num;
 	int preferred_slot;
 	int s_sectsize_bits;