message: Reset PTO timer when a Retry is received
  This will require a test, which will follow.
  Closes
diff: @@ -607,6 +607,7 @@ impl LossRecovery {
  /// When receiving a retry, get all the sent packets so that they can be flushed.
  /// We also need to pretend that they never happened for the purposes of congestion control.
  pub fn retry(&mut self) -> Vec<SentPacket> {
  + self.pto_state = None;
  let cc = &mut self.cc;
  self.spaces
  .iter_mut()
  