Fix tcp-highwater initial value

Fix tcp-highwater initial value

During BIND startup it scans for network interfaces available, in this
process it ensures that for every interface it will bind and listen to,
at least one socket will be always available accepting connections on
that interface, this way avoiding some DOS attacks that could exploit
tcp quota on some interface and make others unavailable.

In the previous network implementation this initial "reserved" tcp-quota
used by BIND was already been added to the tcp-highwater stats, but with
the new network code it was necesary to add this workaround to ensure
tcp-highwater stats reflect the tcp-quota used by BIND after startup.