Make client keep track of originalDestinationConnectionId

Summary:
When I tested against picoquic, I found that an exception was thrown here: https://fburl.com/diffusion/qsnzingx.

The reason is that we modify `conn.initialDestinationConnectionId` in the event of a retry, so it's no longer the original destination connection id. By separately keeping track of the original destination connection id, we can solve this issue.

Reviewed By: mjoras

Differential Revision: D23722127

fbshipit-source-id: 94be08812e675feaf46f5af86e7304af84c1910c

quic/client/state/ClientStateMachine.cpp

@@ -30,6 +30,8 @@ std::unique_ptr<QuicClientConnectionState> undoAllClientStateForRetry(
   newConn->clientConnectionId = conn->clientConnectionId;
   newConn->initialDestinationConnectionId =
       conn->initialDestinationConnectionId;
+  newConn->originalDestinationConnectionId =
+      conn->originalDestinationConnectionId;
   // TODO: don't carry server connection id over to the new connection.
   newConn->serverConnectionId = conn->serverConnectionId;
   newConn->ackStates.initialAckState.nextPacketNum =
@@ -100,7 +102,7 @@ void processServerInitialParams(
         initialSourceConnId.value() !=
             conn.readCodec->getServerConnectionId() ||
         originalDestinationConnId.value() !=
-            conn.initialDestinationConnectionId) {
+            conn.originalDestinationConnectionId) {
       throw QuicTransportException(
           "Initial CID does not match.",
           TransportErrorCode::TRANSPORT_PARAMETER_ERROR);