ipatests: xfail for test_ipahealthcheck_hidden_replica to respect pki version
    
    Change xfail for test_replica_promotion.py/TestHiddenReplicaPromotion/test_ipahealthcheck_hidden_replica
    to respect platform and pki version as the related issue is fixed.
    
    Implement tasks/get_platform_version which returns a platform version
    number(s) of a provided host in a form of a tuple.
    
    Related: https://pagure.io/freeipa/issue/8582
    
    Signed-off-by: Michal Polovka <mpolovka@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>