Rewrite _bound_size() to bound_size() in storage_utils.py
    
    Fix a bug where the possibility of maxSize() being 0, a value which is used
    to mean no maxSize() given, is not taken into account.
    
    Since, a fall back is needed in case this happens, pass old_size to
    _bound_size as well.
    
    Rearrange if statement a bit to make it clearer now that additional
    possibilities are taken into account.
    
    Do a bit more logging, in case something useful-to-know or bad happens.
    
    Signed-off-by: mulhern <amulhern@redhat.com>