Implement S3-HDFS gateway (#7440)

- [x] Support bucket and regular object operations
- [x] Supports Select API on HDFS
- [x] Implement multipart API support
- [x] Completion of ListObjects support

cmd/disk-cache-fs.go

@@ -87,7 +87,7 @@ func newCacheFSObjects(dir string, expiry int, maxDiskUsagePct int) (*cacheFSObj
 			readersMap: make(map[string]*lock.RLockedFile),
 		},
 		nsMutex:       newNSLock(false),
-		listPool:      newTreeWalkPool(globalLookupTimeout),
+		listPool:      NewTreeWalkPool(globalLookupTimeout),
 		appendFileMap: make(map[string]*fsAppendFile),
 	}