private Path getZooKeeperAppPath(String trailingPath) {
            if (trailingPath == null) return sessionPath;

            return sessionPath.append(trailingPath);
        }
Gets a full ZK application path

@param trailingPath trailing part of path to be appended to ZK app path
@return a String with the full ZK application path including trailing path, if set
configserver/src/main/java/com/yahoo/vespa/config/server/deploy/ZooKeeperDeployer.java