Wait for ostree to be signed before using it
    
    Images should include signed bits, so we need to block the compose until
    the commit is signed.
    
    Related: https://pagure.io/pungi/issue/650
    Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>
    
    (cherry picked from commit 968f8fdf5222696c2b075a0325c844032ba8d427)
    
    Signed-off-by: Dusty Mabe <dusty@dustymabe.com>