Don't backup nss.conf on upgrade with the switch to mod_ssl
    
    This is because if backed up it may contain IPA-specific entries
    like an import of ipa-rewrite.conf that on uninstall won't exist
    and this will keep Apache from restarting.
    
    We already have a backup of nss.conf from pre-install. Stick with
    that.
    
    Related: https://pagure.io/freeipa/issue/3757
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Stanislav Laznicka <slaznick@redhat.com>
    Reviewed-By: Rob Crittenden <rcritten@redhat.com>