filer: processing all response headers, no pass through to volume server

* filer calculate MD5 etag
* filer handle response headers, instread of pass it to volume servers

weed/storage/needle/crc.go

@@ -1,11 +1,11 @@
 package needle
 
 import (
-	"crypto/md5"
 	"fmt"
 
-	"github.com/chrislusf/seaweedfs/weed/util"
 	"github.com/klauspost/crc32"
+
+	"github.com/chrislusf/seaweedfs/weed/util"
 )
 
 var table = crc32.MakeTable(crc32.Castagnoli)
@@ -29,13 +29,3 @@ func (n *Needle) Etag() string {
 	util.Uint32toBytes(bits, uint32(n.Checksum))
 	return fmt.Sprintf("%x", bits)
 }
-
-func (n *Needle) MD5() string {
-
-	hash := md5.New()
-
-	hash.Write(n.Data)
-
-	return fmt.Sprintf("%x", hash.Sum(nil))
-
-}