Subnet comparison is broken

[LeeSmet]

Currently subnet derives PartialEq (and the inner type does so as well). This means equality checks are done based on the actual in memory data. In practice, we want equality checks based on the prefix only. Fixing this should fix seqno requests not being handled by peers as well. It does mean that 2 subnets differing only in the IP which is not part of the subnet, will be considered equal. Since we talk about a subnet here, that is fine.