remove unused code

weed/storage/volume_read.go

@@ -4,7 +4,6 @@ import (
 	"fmt"
 	"github.com/seaweedfs/seaweedfs/weed/util/mem"
 	"io"
-	"sync"
 	"time"
 
 	"github.com/seaweedfs/seaweedfs/weed/glog"
@@ -190,14 +189,6 @@ func (v *Volume) readNeedleDataInto(n *needle.Needle, readOption *ReadOption, wr
 
 }
 
-func synchronizedRead(rwLock *sync.RWMutex, enabled bool, closure func() error) error {
-	if enabled {
-		rwLock.RLock()
-		defer rwLock.RUnlock()
-	}
-	return closure()
-}
-
 func min(x, y int) int {
 	if x < y {
 		return x