async: don't reply to heartbeat frames
async: don't reply to heartbeat frames

We're supposed to send heartbeat frames on a regular basis (which we do)
and receive some on the same regular basis, but not answer to the ones we receive.

Eventually we should check that we got the heartbeat from the server at the right pace

Signed-off-by: Marc-Antoine Perennou <07f76cf0511c79b361712839686f3cee8c75791c@Perennou.com>

sozu-proxy/lapin,swizard0/lapin,Geal/lapin,swizard0/lapin,Geal/lapin,Keruspe/lapin,Keruspe/lapin