Hotfix for missing storage in payload class (#1271657)
    
    The problem here is that payload is setting up storage when
    PayloadManager run a thread but the user could do steps which
    will call the spaceRequired() method sooner.
    
    Now the behavior is the same as it was with the old spaceRequired
    method for the variant when storage is not set.
    
    Resolves: rhbz#1271657