void initialize() {
            curator.create(sessionPath);

            for (String subPath : List.of(DEFCONFIGS_ZK_SUBPATH,
                                          USER_DEFCONFIGS_ZK_SUBPATH,
                                          USERAPP_ZK_SUBPATH,
                                          ZKApplicationPackage.fileRegistryNode)) {
                // TODO: The replaceFirst below is hackish.
                curator.create(getZooKeeperAppPath().append(subPath.replaceFirst("/", "")));
            }
        }
Sets up basic node structure in ZooKeeper and purges old data.
This is the first operation on ZK during deploy.
configserver/src/main/java/com/yahoo/vespa/config/server/deploy/ZooKeeperDeployer.java