NFSv4.1: Add tracepoints for debugging slot table operations

Add tracepoints to nfs41_setup_sequence and nfs41_sequence_done
to track session and slot table state changes.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c
index c074930..b25ed7e 100644
--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -464,6 +464,7 @@
 	} else
 		res->csr_status = status;
 
+	trace_nfs4_cb_sequence(args, res, status);
 	dprintk("%s: exit with status = %d res->csr_status %d\n", __func__,
 		ntohl(status), ntohl(res->csr_status));
 	return status;