Reduce Asgard disk size
    
    Upon enrolling Orbit hypervisors in Salt it was found that the
    is-size of the Asgard root disks is larger than the actual size.
    Since the additional space is not needed, avoid unnecessary
    block device resizing.
    
    Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>