ipa-server-upgrade: fix add_systemd_user_hbac
    
    During upgrade, the method add_systemd_user_hbac is creating
    a hbacsvc and a hbacrule, but fails in python2 because of
    unicode conversion errors.
    The arguments should be defined as u'value'.
    
    Fixes: https://pagure.io/freeipa/issue/7896
    Reviewed-By: Christian Heimes <cheimes@redhat.com>