clarkb: fungi  hi, when build image have follow error , I try add block-device-efi element, it didn't work.
```
DEBUG diskimage_builder.block_device.utils [-] exec_sudo: /var/cache/nodepool/dib_tmp/dib_build.09t1RZhC/mnt/: 1.7 GiB (1827090432 bytes) trimmed exec_sudo /usr/lib/python3.6/site-packages/diskimage_builder/block_device/utils.py:135
INFO diskimage_builder.block_device.utils [-] Calling [sudo umount /var/cache/nodepool/dib_tmp/dib_build.09t1RZhC/mnt/]
INFO diskimage_builder.block_device.utils [-] Calling [sudo kpartx -d /dev/loop1]
DEBUG diskimage_builder.block_device.utils [-] exec_sudo: device-mapper: remove ioctl on loop1p3  failed: Device or resource busy exec_sudo /usr/lib/python3.6/site-packages/diskimage_builder/block_device/utils.py:135
```
diskimage configure like
```
diskimages:
  - name: ubuntu-focal
    pause: false
    rebuild-age: 172800
    elements:
      - block-device-efi
      - vm
      - simple-init
      - nodepool-base
      - cache-devstack
      - growroot
      - infra-package-needs
      - ubuntu-minimal
    release: focal
    username: zuul
    env-vars:
      TMPDIR: /opt/dib_tmp
      DIB_CHECKSUM: '1'
      DIB_IMAGE_CACHE: /opt/dib_cache
      DIB_APT_LOCAL_CACHE: '0'
      DIB_DISABLE_APT_CLEANUP: '0'
      DIB_DEBOOTSTRAP_EXTRA_ARGS: '--no-check-gpg'
      DIB_DEBIAN_COMPONENTS: 'main,universe'
      DIB_CUSTOM_PROJECTS_LIST_URL: 'file:///etc/nodepool/repos.yaml'
      GIT_HTTP_LOW_SPEED_TIME: '600'
      GIT_HTTP_LOW_SPEED_LIMIT: '1000'
```