Log Message:
mysql57-server & mysql80-server: correct MESSAGE

As of MySQL 5.7, installations created using --initialize no longer
have an empty root password; one is generated as part of the process
and marked expired. (This message is in part simply advice to read the
documentation. However, it's possible other downstream packagers use
--initialize-insecure instead, which retains the old empty password
approach, so this could be a pkgsrc-specific detail to consider.)