quic: compute retransmission timeout correctly

Previously, if the expiry timestamp was in the future by less
than 1ms, the retransmission timer would not have been scheduled.

(This also removes an unused line from the test that this
problem made flaky.)

PR-URL: #157
Reviewed-By: James M Snell <[email protected]>

Author: addaleax

src/node_quic_session.cc

@@ -1291,7 +1291,8 @@ void QuicSession::RemoveStream(int64_t stream_id) {
 void QuicSession::ScheduleRetransmit() {
   uint64_t now = uv_hrtime();
   uint64_t expiry = ngtcp2_conn_get_expiry(Connection());
-  uint64_t interval = (expiry < now) ? 1 : ((expiry - now) / 1000000UL);
+  uint64_t interval = (expiry - now) / 1000000UL;
+  if (expiry < now || interval == 0) interval = 1;
   Debug(this, "Scheduling the retransmit timer for %" PRIu64, interval);
   UpdateRetransmitTimer(interval);
 }

test/parallel/test-quic-packetloss.js

@@ -1,4 +1,3 @@
-// Flags: --expose-internals
 'use strict';
 
 // This test is not yet working correctly because data