ipatests: refactor test_ipa_cert_fix with tasks
    
    Fixes: https://pagure.io/freeipa/issue/8932
    Signed-off-by: François Cami <fcami@redhat.com>
    Reviewed-By: Michal Polovka <mpolovka@redhat.com>
    Reviewed-By: Armando Neto <abiagion@redhat.com>
    Reviewed-By: Mohammad Rizwan <myusuf@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>