Remove "logger" field from config.json (#5268)

File logging removed as part of improvement to server logging.

config.json format updated to version 21.

Fixes #5176

cmd/logger.go

@@ -22,7 +22,6 @@ import (
 	"path"
 	"runtime"
 	"strings"
-	"sync"
 
 	"github.com/Sirupsen/logrus"
 	"github.com/minio/mc/pkg/console"
@@ -31,52 +30,6 @@ import (
 
 var log = NewLogger()
 
-type loggers struct {
-	sync.RWMutex
-	Console ConsoleLogger `json:"console"`
-	File    FileLogger    `json:"file"`
-}
-
-// Validate - Check whether loggers are valid or not.
-func (l *loggers) Validate() (err error) {
-	if l != nil {
-		fileLogger := l.GetFile()
-		if fileLogger.Enable && fileLogger.Filename == "" {
-			err = fmt.Errorf("Missing filename for enabled file logger")
-		}
-	}
-
-	return err
-}
-
-// SetFile set new file logger.
-func (l *loggers) SetFile(flogger FileLogger) {
-	l.Lock()
-	defer l.Unlock()
-	l.File = flogger
-}
-
-// GetFileLogger get current file logger.
-func (l *loggers) GetFile() FileLogger {
-	l.RLock()
-	defer l.RUnlock()
-	return l.File
-}
-
-// SetConsole set new console logger.
-func (l *loggers) SetConsole(clogger ConsoleLogger) {
-	l.Lock()
-	defer l.Unlock()
-	l.Console = clogger
-}
-
-// GetConsole get current console logger.
-func (l *loggers) GetConsole() ConsoleLogger {
-	l.RLock()
-	defer l.RUnlock()
-	return l.Console
-}
-
 // LogTarget - interface for log target.
 type LogTarget interface {
 	Fire(entry *logrus.Entry) error