ConfigurationGenerator.checkDatabaseConnection() must use customized nuxeo.db.jdbc.url if exists

If nuxeo.db.jdbc.url is customized, it is not used by org.nuxeo.launcher.config.ConfigurationGenerator.checkDatabaseConnection(String, String, String, String, String, String) which always uses the one from the template, replacing the variables with values from nuxeo.db.host, nuxeo.db.port and nuxeo.db.name.