Warn when mariadb password differs from environment variable

[rocketeerbkw]

During the setup entrypoint, we should output a log message if we can detect that the password set in the environment variable doesn't match what is currently set for the mariadb user.

This would help debug issues when, for example, a secret has changed in kubernetes and now an application doesn't have permission to access the database.

[smlx]

If the entrypoint exited with an error in this case then the problem would be visible at the k8s API level instead of needing to check logs.