* hi，when I use nodepool DIB build unbuntu-focal image occur error.https://bugs.launchpad.net/diskimage-builder/+bug/1969093

```
2022-04-13 08:42:56.123 | INFO diskimage_builder.block_device.utils [-] Calling [sudo umount /var/cache/nodepool/dib_tmp/dib_build.3DMuQbbI/mnt/]
2022-04-13 08:42:56.675 | INFO diskimage_builder.block_device.utils [-] Calling [sudo kpartx -d /dev/loop0]
2022-04-13 08:42:56.715 | DEBUG diskimage_builder.block_device.utils [-] exec_sudo: device-mapper: remove ioctl on loop0p1 failed: Device or resource busy exec_sudo /usr/lib/python3.6/site-packages/diskimage_builder/block_device/utils.py:135
```

I found after build. df -h still have /dev/mapper/loop0p1 like follow. if I run unmount /run/media/root/cloudimg-rootfs,then `kpartx -d /dev/loop0` would be success. Does this need to be unmount. but I don't found unmount /root/media/root/clouding-rootfs on elements script.

```
[root@managesf.sftests.com /]# df -h
Filesystem               Size  Used Avail Use% Mounted on
devtmpfs                  16G     0   16G   0% /dev
tmpfs                     16G   20K   16G   1% /dev/shm
tmpfs                     16G   19M   16G   1% /run
tmpfs                     16G     0   16G   0% /sys/fs/cgroup
/dev/mapper/centos-root  863G   33G  831G   4% /
/dev/sda2               1014M  154M  861M  16% /boot
/dev/sda1                200M   12M  189M   6% /boot/efi
/dev/mapper/centos-home   50G   58M   50G   1% /home
tmpfs                    3.1G   52K  3.1G   1% /run/user/0
/dev/mapper/loop0p1      3.8G  2.0G  1.6G  57% /run/media/root/cloudimg-rootfs
```