objectLayer: Check for format.json in a wrapped disk. (#3311)

This is needed to validate if the `format.json` indeed exists
when a fresh node is brought online.

This wrapped implementation also connects to the remote node
by attempting a re-login. Subsequently after a successful
connect `format.json` is validated as well.

Fixes #3207

cmd/logger-file-hook.go

@@ -68,7 +68,7 @@ func (l *localFile) Fire(entry *logrus.Entry) error {
 	if err != nil {
 		return fmt.Errorf("Unable to read entry, %v", err)
 	}
-	l.File.Write([]byte(line + "\n"))
+	l.File.Write([]byte(line))
 	l.File.Sync()
 	return nil
 }