protect tracker copy properly to avoid race (#18984)

```
WARNING: DATA RACE
Write at 0x00c000aac1e0 by goroutine 1133:
  github.com/minio/minio/cmd.(*healingTracker).updateProgress()
      github.com/minio/minio/cmd/background-newdisks-heal-ops.go:183 +0x117
  github.com/minio/minio/cmd.(*erasureObjects).healErasureSet.func5()
      github.com/minio/minio/cmd/global-heal.go:292 +0x1d3

Previous read at 0x00c000aac1e0 by goroutine 1003:
  github.com/minio/minio/cmd.(*allHealState).updateHealStatus()
      github.com/minio/minio/cmd/admin-heal-ops.go:136 +0xcb
  github.com/minio/minio/cmd.(*healingTracker).save()
      github.com/minio/minio/cmd/background-newdisks-heal-ops.go:223 +0x424
```

buildscripts/rewrite-old-new.sh

@@ -87,7 +87,7 @@ function verify_rewrite() {
 		exit 1
 	fi
 
-	go install github.com/minio/minio/docs/debugging/s3-check-md5@latest
+	go install github.com/minio/minio/docs/debugging/s3-check-md5@master
 	if ! s3-check-md5 \
 		-debug \
 		-versions \