Minor fix, TODO comment

Minor fix, TODO comment

Recent changes caused a packet timeout to be either 1 second or double
the heartbeat interval time (the maximum of the two). This is kind of a
problem since packet timeout should be ideally decided based on the
peer's heartbeat interval time, not this instance's heartbeat interval
time.

Some "scaffolding" code should be added:

  - Heartbeat packets should send the current instance's heartbeat
    interval time.
  - Max capacity of cached sent packets should be increased based on
    the peer's heartbeat interval and the rate of received non-heartbeat
    packets.
  - Maybe have a function to tell UDPC the intended usage regarding
    latency: focus on low-latency default behavior, or focus on high
    latency low packet-send-rate behavior.

The current changes should be reverted on master and the new changes
should be held back for now until this is all set up.