ipa-client-install: use the authselect backup during uninstall
    
    When ipa-client-install is run on a system with no existing
    authselect configuration (for instance a fedora 31 new install),
    uninstallation is picking sssd profile but this may lead to
    a configuration with differences compared to the pre-ipa-client
    state.
    
    Now that authselect provides an option to backup the existing
    configuration prior to setting a profile, the client install
    can save the backup name and uninstall is able to apply the
    backup in order to go back to the pre-ipa-client state.
    
    Fixes: https://pagure.io/freeipa/issue/8189
    Reviewed-By: Michal Polovka <mpolovka@redhat.com>
    Reviewed-By: Francois Cami <fcami@redhat.com>