zebra: make ZEBRA_FLAG_CHANGED internal status

This flag is used internally in zebra only. And it makes no sense
to expose it over the zclient API, as having it set from client
could corrupt the internal state.

Signed-off-by: Timo Teräs <timo.teras@iki.fi>
Acked-by: Donald Sharp <sharpd@cumulusnetworks.com>
diff --git a/zebra/rib.h b/zebra/rib.h
index 2af90db..6e0966a 100644
--- a/zebra/rib.h
+++ b/zebra/rib.h
@@ -78,6 +78,7 @@
   /* RIB internal status */
   u_char status;
 #define RIB_ENTRY_REMOVED	(1 << 0)
+#define RIB_ENTRY_CHANGED	(1 << 1)
 
   /* Nexthop information. */
   u_char nexthop_num;