Subnets endpoint doesn't normalize country codes before lookup

At some point in the last few months, the api.eclipse.org/geoip/subnets/ipv4/* endpoint broke and always returns an empty list. We'll need to look into what changed upstream to see why the map isn't properly populating at this point.

@mward as someone with closer eyes on infra, do you know if we use that endpoint anywhere? The /geoip/cities/* and /geoip/countries/* endpoints still respond as expected just to be clear.