ipatests: Clean up existing ACME registration and certs
    
    The same base class is used for ACME setup and configuration.
    Be sure to clean up any existing registraton prior to continuing
    otherwise ACME register will complain.
    
    https://pagure.io/freeipa/issue/8581
    
    Signed-off-by: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Mohammad Rizwan <myusuf@redhat.com>
    Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>
    Reviewed-By: Armando Neto <abiagion@redhat.com>