Set new PARALLEL_CANCEL_WHOLE_CLUSTER for all parallel parents
    
    This is the magic variable to disable openQA's "cancel whole
    cluster on child failure" behaviour that I'm adding in
    https://github.com/os-autoinst/openQA/pull/2017 . We want it
    set for all parallel parent suites in Fedora.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>