new dib-block-device code fails - mismatched arguments

[Ramon Buckland]

A portion of the cleanup code calls the new "dib-block-device"

master branch

From:
diskimage-builder/blob/master/diskimage_builder/lib/img-functions#L52

```
function cleanup () {
    DIB_BLOCK_DEVICE_SCRIPT=$(which dib-block-device)
    sudo -E ${DIB_BLOCK_DEVICE_SCRIPT} \
         --phase=umount \
         --build-dir="${TMP_BUILD_DIR}"
    unmount_image
    cleanup_build_dir
    cleanup_image_dir
}
```

But the arguments for `dib-block-device` do not support --build-dir, and in addition requires --params.

```
usage: dib-block-device [-h] --phase PHASE --params PARAMS [--symbol SYMBOL]
dib-block-device: error: unrecognized arguments: --build-dir=/tmp/dib_build.4igGUW9K
```