Avoid using fastjson parser pool, move back to jsoniter (#8190)

It looks like from implementation point of view fastjson
parser pool doesn't behave the same way as expected
when dealing many `xl.json` from multiple disks.

The fastjson parser pool usage ends up returning incorrect
xl.json entries for checksums, with references pointing
to older entries. This led to the subtle bug where checksum
info is duplicated from a previous xl.json read of a different
file from different disk.

cmd/config.go

@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"fmt"
 	"path"
 	"runtime"
 	"strings"
@@ -136,18 +137,23 @@ func (sys *ConfigSys) Init(objAPI ObjectLayer) error {
 	//    of the object layer.
 	//  - Write quorum not met when upgrading configuration
 	//    version is needed.
-	for range newRetryTimerSimple(doneCh) {
-		if err := initConfig(objAPI); err != nil {
-			if strings.Contains(err.Error(), InsufficientReadQuorum{}.Error()) ||
-				strings.Contains(err.Error(), InsufficientWriteQuorum{}.Error()) {
-				logger.Info("Waiting for configuration to be initialized..")
-				continue
+	retryTimerCh := newRetryTimerSimple(doneCh)
+	for {
+		select {
+		case <-retryTimerCh:
+			if err := initConfig(objAPI); err != nil {
+				if strings.Contains(err.Error(), InsufficientReadQuorum{}.Error()) ||
+					strings.Contains(err.Error(), InsufficientWriteQuorum{}.Error()) {
+					logger.Info("Waiting for configuration to be initialized..")
+					continue
+				}
+				return err
 			}
-			return err
+			return nil
+		case <-globalOSSignalCh:
+			return fmt.Errorf("Initializing config sub-system gracefully stopped")
 		}
-		break
 	}
-	return nil
 }
 
 // NewConfigSys - creates new config system object.