prci: run full external_ca test suite
    
    Before this patch there was just one test in external_ca suite,
    now we add one new test class thus deleting the specific class
    in external_ca PRCI section.
    
    https://pagure.io/freeipa/issue/7302
    
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>