.minio.sys should be skipped on rm

[zhoucheng361]

https://github.com/juicedata/juicefs/actions/runs/9229327804/job/25395313586

df -lh
  echo "juicefs log"
  sudo rm -rf /mnt/data
  sudo tail -n 1000 /var/log/juicefs.log
  grep "<FATAL>:" /var/log/juicefs.log && exit 1 || true
  shell: /usr/bin/bash -e {0}
Filesystem      Size  Used Avail Use% Mounted on
/dev/root        7[3](https://github.com/juicedata/juicefs/actions/runs/9229327804/job/25395313586#step:11:3)G   46G   28G  63% /
devtmpfs        7.9G     0  7.9G   0% /dev
tmpfs           7.9G  [4](https://github.com/juicedata/juicefs/actions/runs/9229327804/job/25395313586#step:11:4).0K  7.9G   1% /dev/shm
tmpfs           1.6G  1.3M  1.6G   1% /run
tmpfs           [5](https://github.com/juicedata/juicefs/actions/runs/9229327804/job/25395313586#step:11:5).0M     0  5.0M   0% /run/lock
tmpfs           7.9G     0  7.9G   0% /sys/fs/cgroup
/dev/sda15      105M  [6](https://github.com/juicedata/juicefs/actions/runs/9229327804/job/25395313586#step:11:6).1M   99M   6% /boot/efi
/dev/loop0       64M   64M     0 100% /snap/core20/2264
/dev/loop2       39M   39M     0 100% /snap/snapd/21465
/dev/loop1       92M   92M     0 100% /snap/lxd/24061
/dev/sdb1        [7](https://github.com/juicedata/juicefs/actions/runs/9229327804/job/25395313586#step:11:7)4G   17G   53G  25% /mnt
tmpfs           1.6G     0  1.6G   0% /run/user/1001
juicefs log
rm: cannot remove '/mnt/data/.minio.sys': Directory not empty
Error: Process completed with exit code 1.

[zhoucheng361]

.minio.sys maybe deleted when user want to rebuild IAM.