message: update autoix-mempool.py to test both "old" and "new" InstantSend (and fix CheckCanLock to respect mempool limits)
diff: @@ -137,6 +137,10 @@ bool CInstantSendManager::ProcessTx(CNode* pfrom, const CTransaction& tx, CConnm
  bool CInstantSendManager::CheckCanLock(const CTransaction& tx, bool printDebug, const Consensus::Params& params)
  {
  + if (sporkManager.IsSporkActive(SPORK_16_INSTANTSEND_AUTOLOCKS) && (mempool.UsedMemoryShare() > CInstantSend::AUTO_IX_MEMPOOL_THRESHOLD)) {
  + return false;
  + }
  +
  int nInstantSendConfirmationsRequired = params.nInstantSendConfirmationsRequired;
  uint256 txHash = tx.GetHash();
  