message: rpc/blockchain.cpp: Remove g_utxosetscan mutex that is only protecting a single atomic variable
diff: @@ -1874,7 +1874,6 @@ bool FindScriptPubKey(std::atomic<int>& scan_progress, const std::atomic<bool>&
  }
  /** RAII object to prevent concurrency issue when scanning the txout set */
  -static std::mutex g_utxosetscan;
  static std::atomic<int> g_scan_progress;
  static std::atomic<bool> g_scan_in_progress;
  static std::atomic<bool> g_should_abort_scan;
  @@ -1887,18 +1886,15 @@ public:
  bool reserve() {
  CHECK_NONFATAL(!m_could_reserve);
  - std::lock_guard<std::mutex> lock(g_utxosetscan);
  - if (g_scan_in_progress) {
  + if (g_scan_in_progress.exchange(true)) {
  return false;
  }
  - g_scan_in_progress = true;
  m_could_reserve = true;
  return true;
  }
  ~CoinsViewScanReserver() {
  if (m_could_reserve) {
  - std::lock_guard<std::mutex> lock(g_utxosetscan);
  g_scan_in_progress = false;
  }
  }
  