batch: account for auto-binding in server context
    
    When batch runs under server context, we have no context.principal set
    because we talk directly to LDAPI endpoint and authenticate using
    auto-binding, not GSSAPI. Account to that in the logger.
    
    Fixes: https://pagure.io/freeipa/issue/9583
    
    Signed-off-by: Alexander Bokovoy <abokovoy@redhat.com>
    Reviewed-By: Thomas Woerner <twoerner@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>
    Reviewed-By: Rafael Guterres Jeffman <rjeffman@redhat.com>