fix ipv6 file timestamp calculation

fix ipv6 file timestamp calculation

NOTE: ipv4 database no longer updated, stays with March 2018 GeoLite Legacy builds

https://dev.maxmind.com/geoip/legacy/geolite/

Updated versions of the GeoLite Legacy databases are now only available
to redistribution license customers, although anyone can continue to
download the March 2018 GeoLite Legacy builds. Starting January 2, 2019,
the last build will be removed from our website. GeoLite Legacy database
users will need to switch to the GeoLite2 or commercial GeoIP databases
and update their integrations by January 2, 2019.