message: net: fix a few cases where messages were sent rather than dropped upon disconnection
  coming from btc@905bc68d05595f41cca36b3df83accd10c00cc48
diff: @@ -6103,7 +6103,7 @@ bool SendMessages(CNode* pto)
  // Ping automatically sent as a latency probe & keepalive.
  pingSend = true;
  }
  - if (pingSend) {
  + if (pingSend && !pto->fDisconnect) {
  uint64_t nonce = 0;
  while (nonce == 0) {
  GetRandBytes((unsigned char*)&nonce, sizeof(nonce));
  @@ -6177,7 +6177,7 @@ bool SendMessages(CNode* pto)
  if (pindexBestHeader == NULL)
  pindexBestHeader = chainActive.Tip();
  bool fFetch = state.fPreferredDownload || (nPreferredDownload == 0 && !pto->fClient && !pto->fOneShot); // Download if this is a nice peer, or we have no nice peers and this one might do.
  - if (!state.fSyncStarted && !pto->fClient && fFetch /*&& !fImporting*/ && !fReindex) {
  + if (!state.fSyncStarted && !pto->fClient && !pto->fDisconnect && fFetch /*&& !fImporting*/ && !fReindex) {
  // Only actively request headers from a single peer, unless we're close to end of initial download.
  if (nSyncStarted == 0 || pindexBestHeader->GetBlockTime() > GetAdjustedTime() - 6 * 60 * 60) { // NOTE: was "close to today" and 24h in Bitcoin
  state.fSyncStarted = true;
  