st: also check _NEW_PROGRAM flag for vertex shader constant buffers

This is a follow-on to commit c1a3b85280.
Note that (at this time) wherever _NEW_PROGRAM_CONSTANTS is set we're still
setting _NEW_PROGRAM so this won't really make any difference (for now).

src/mesa/state_tracker/st_atom_constbuf.c

@@ -105,7 +105,7 @@ static void update_vs_constants(struct st_context *st )
 const struct st_tracked_state st_update_vs_constants = {
    "st_update_vs_constants",				/* name */
    {							/* dirty */
-      _NEW_PROGRAM_CONSTANTS,
+      (_NEW_PROGRAM | _NEW_PROGRAM_CONSTANTS),          /* mesa */
       ST_NEW_VERTEX_PROGRAM,				/* st */
    },
    update_vs_constants					/* update */