drbd: Implemented two new connection states Ahead/Behind

In this connection mode, the ahead node no longer replicates
application IO. The behind's disk becomes out dated.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index c804e44..21b7439 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -2217,6 +2217,8 @@
 	case C_VERIFY_T:
 	case C_PAUSED_SYNC_S:
 	case C_PAUSED_SYNC_T:
+	case C_AHEAD:
+	case C_BEHIND:
 		/* maybe stable, look at the disk state */
 		break;