Remove DL0 specific code from ipa-ca-install
    
    Replica files are DL0 specific therefore all the code that is related to
    replica files have been removed. An additional check for the new minimal
    domain level has been added.
    
    See: https://pagure.io/freeipa/issue/7689
    Signed-off-by: Thomas Woerner <twoerner@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Christian Heimes <cheimes@redhat.com>