Remove unused images

    verbose : boolean (False)
        toggle verbose output

    CLI Example:

    .. code-block:: bash

        salt '*' imgadm.vacuum [verbose=True]

def vacuum(verbose=False):
    '''
    Remove unused images

    verbose : boolean (False)
        toggle verbose output

    CLI Example:

    .. code-block:: bash

        salt '*' imgadm.vacuum [verbose=True]
    '''
    ret = {}
    cmd = 'imgadm vacuum -f'
    res = __salt__['cmd.run_all'](cmd)
    retcode = res['retcode']
    if retcode != 0:
        ret['Error'] = _exit_status(retcode)
        return ret
    # output: Deleted image d5b3865c-0804-11e5-be21-dbc4ce844ddc (lx-centos-6@20150601)
    result = {}
    for image in res['stdout'].splitlines():
        image = [var for var in image.split(" ") if var]
        result[image[2]] = {
            'name': image[3][1:image[3].index('@')],
            'version': image[3][image[3].index('@')+1:-1]
        }
    if verbose:
        return result
    else:
        return list(result.keys())