[Swan-dev] ikev2: only count empty informational messages as liveness probes

[Paul Wouters]

commit b6e986fb7181fe6288dbba3fb98832b53aee1415
Author: Andrew Cagney <cagney at gnu.org>
Date:   Thu May 20 11:21:33 2021 -0400

     ikev2: only count empty informational messages as liveness probes

     was including informational messages with notify payloads



This is not correct through. Any informational message can contain
notify payloads. In theory they should all include NAT detection
payloads in case a NAT appeared out of nowhere.

But also, every exchange message that proved it is a new sequence number
counts as "liveness probe". So if a REKEY happens, the "liveness" should
also be updated.

Paul