vty/auth: Make sure we clear the last tuple when changing auth params

If the Ki or auth algo changes, chances are that the last tuple cannot
be used anymore, so clear it.

Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
diff --git a/openbsc/src/vty_interface_layer3.c b/openbsc/src/vty_interface_layer3.c
index bf88fc0..b5af0ab 100644
--- a/openbsc/src/vty_interface_layer3.c
+++ b/openbsc/src/vty_interface_layer3.c
@@ -485,6 +485,9 @@
 		return CMD_WARNING;
 	}
 
+	/* the last tuple probably invalid with the new auth settings */
+	db_sync_lastauthtuple_for_subscr(NULL, subscr);
+
 	return rc ? CMD_WARNING : CMD_SUCCESS;
 }