Fix tcp-highwater stats updating

Fix tcp-highwater stats updating

After the network manager rewrite, tcp-higwater stats was only being
updated when a valid DNS query was received over tcp.

It turns out tcp-quota is updated right after a tcp connection is
accepted, before any data is read, so in the event that some client
connect but don't send a valid query, it wouldn't be taken into
account to update tcp-highwater stats, that is wrong.

This commit fix tcp-highwater to update its stats whenever a tcp connection
is established, independent of what happens after (timeout/invalid
request, etc).