vty/logging: ensure consistent '%' prefix for warnings

Change-Id: I2b2bab61e46668c3b4b0ccad88d02b6d00a83544
diff --git a/tests/logging/logging_vty_test.vty b/tests/logging/logging_vty_test.vty
index 91c2a48..30e73ab 100644
--- a/tests/logging/logging_vty_test.vty
+++ b/tests/logging/logging_vty_test.vty
@@ -29,7 +29,7 @@
 logging_vty_test(config)# exit
 
 logging_vty_test# logging level force-all notice
-Logging was not enabled.
+% Logging was not enabled.
 
 logging_vty_test# logging enable
 logging_vty_test# logging filter all 1