DNSSEC: backup and restore opendnssec zone list file
When zone list is not restored after unninstall, this may slow down
enbaling DNSSEC signing for zones and print unwanted
errors into log after new installation.
Related to: https://fedorahosted.org/freeipa/ticket/5273
Reviewed-By: Petr Spacek <pspacek@redhat.com>