@Override
    public void awaitShutdown() {
        fileDownloader.close();
        super.awaitShutdown();
    }
Verifies that all active sessions has an application package on local disk.
If not, the package is downloaded with file distribution. This can happen e.g.
if a config server is down when the application is deployed. This maintainer should only be run
if there is more than 1 config server

@author gjoranv
configserver/src/main/java/com/yahoo/vespa/config/server/maintenance/ApplicationPackageMaintainer.java