Adjust tests for update and workaround repos provided as ISO
    
    I'm attempting a new approach to the update and workaround repos.
    Instead of having each update test recreate them for itself -
    which is slow and wastes bandwidth - the dispatcher will create
    an ISO at test schedule time and pass it as ISO_2. Then the test
    just mounts the ISO. This makes the necessary adjustments on the
    test side.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>