Remove DL0 specific code from cainstance and ca in ipaserver/install
    
    cainstance.replica_ca_install_check is only used in ca.install_check if
    replica_config is not None (replica installation). As it is immediately
    stopped if promote is not set, therefore it can be removed.
    
    The check for cafile in ca.install_check has been dropped. promote is set
    to True in ca.install_step_0 if replica_config is not None for
    cainstance.configure_instance.
    
    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>