Update example

scripts/mariadb-cluster-create-database-and-grant

@@ -8,7 +8,7 @@ USERNAME="${3}"
 
 function usage() {
 	echo "Usage: ${0} <hostname> <database> <username>"
-	echo "Example: ${0} db-1.example.com"
+	echo "Example: ${0} db-1.example.com database_name username"
 	exit 1
 }
 if [ -z "${HOST}" ]; then