[DLM] fix reference counting

This is a fix for the patch

021d2ff3a08019260a1dc002793c92d6bf18afb6

I left off a dlm_hold_rsb which causes the box to panic if you try to use
debugfs.  This patch fixes the problem.  Sorry about that,

Signed-off-by: Josef Bacik <jwhiter@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/dlm/debug_fs.c

@@ -250,6 +250,7 @@ static int rsb_iter_next(struct rsb_iter *ri)
 			goto top;
                 }
 		ri->rsb = list_entry(ri->next, struct dlm_rsb, res_hashchain);
+		dlm_hold_rsb(ri->rsb);
 		read_unlock(&ls->ls_rsbtbl[i].lock);
 		dlm_put_rsb(old);
 	}