public void startBeforeBootstrap() {
        if (moreThanOneConfigServer())
            maintainers.add(new ApplicationPackageMaintainer(applicationRepository, curator, Duration.ofSeconds(30), fileServer));
        maintainers.add(new TenantsMaintainer(applicationRepository, curator, interval, Clock.systemUTC()));
    }
Maintenance jobs of the config server.
Each maintenance job is a singleton instance of its implementing class, created and owned by this,
and running its own dedicated thread.

@author hmusum
configserver/src/main/java/com/yahoo/vespa/config/server/maintenance/ConfigServerMaintenance.java